Institutions

The definitions of species of Rubrisciurus, Hyosciurus, and Prosciurillus we document here are determined from study of specimens stored in the following institutions: the American Museum of Natural History, New York (AMNH); Academy of Natural Sciences, Philadelphia (ANSP); the Natural History Museum, London (BMNH); Field Museum of Natural History, Chicago (FMNH); Museum Zoologicum Bogoriense, Cibinong, Java (MZB; now the Indonesian National Museum of Natural History; also known as the Research Center in Biology-Lembaga Ilmu Pengetahuan Indonesia); Naturhistorisches Museum Basel, Switzerland (NMB); Nationaal Natuurhistorisch Museum, Leiden (RMNH); Senckenberg Museum, Frankfurt am Main (SMF); Staatliches Naturhistorische Sammlungen Dresden, Museum für Tierkunde (SNSD); National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM); Zoological Museum of the University of Amsterdam (ZMA); Zoologisches Museum und Instituut für Naturkunde der Humboldt-Universität zu Berlin, Berlin (ZMB). Specimens we reference by catalog number in gazetteers, tables, text, and figure legends are preceded by one of these acronyms.

Specimens

For the most part, the voucher specimens consist of standard museum preparations, a stuffed skin and accompanying cranium and mandible, or skin mounted in live pose from which the skull was extracted. Color descriptions for Prosciurillus leucomus, P. weberi, P. rosenbergii, and P. abstrusus are derived from those museum specimens—Musser's fieldwork never took him to the geographic regions where those species reside. Color descriptons of Rubrisciurus rubriventer, Prosciurillus alstoni, P. topapuensis, P. murinus, and the two species of Hyosciurus come from material collected by Musser and from older museum specimens; Musser's field journals (stored in mammalogy archives at AMNH), where he recorded coloration and other details of freshly caught squirrels, were also consulted. Fluid-preserved whole specimens or skinned carcasses were also preserved by Musser in the field where they were initially fixed in 10% formalin, soaked for several days in water, then finally stored in 70% ethanol.

Measurements

Values for external linear dimensions are from two groups of specimens. One consists of samples collected by Musser from forests of Central Sulawesi. For each individual in these lots, he measured total length; length of tail vertebrae (LT), which excluded the long hairs at the end of the tail (descriptions of new species published in the 1800s and early 1900s often included length of tail without the terminal tuft, and length of tail with the terminal spray of hairs); length of hind foot, including claw (LHF); length of ear (LE), from notch to crown, and excluding any distal tuft of hairs. He took these measurements soon after a squirrel was caught, and weighed it at that time to obtain a value for body mass or weight (W, in grams). Values for length of head and body (LHB) employed here were derived by subtracting length of tail vertebrae from total length.

The second group contains specimens in museums caught and prepared by other collectors. They recorded total length, length of tail, length of hind foot, sometimes length of ear, but rarely weight. We used their values for length of tail (tail vertebrae only), length of hind foot and length of ear if present (H.C. Raven, the collector of specimens in USNM, did not measure this dimension), but sometimes with reservations, which are explained in footnotes to relevant tables. We did not use total length if notated on the specimen tags, employing that value only to subtract the value for length of tail from it to obtain an estimate of length of head and body.

In the laboratory, several measurements were made on specimens from both groups. We measured lengths of overfur (LDF) and guard hairs (LGH) on the dorsum near the rump by placing a ruler at a right angle to the skin surface and recording the approximate mark where ends of the bunched hairs rested; the technique is unsophisticated and the results imprecise, but still provide a descriptive estimate of lengths for those pelage constituents.

Using dial calipers graduated to tenths of millimeters, we measured the following cranial and dental dimensions (listed in their order of appearance, as acronyms, in the tables; limits are illustrated in fig. 1):

Fig. 1

Diagrams (above and at right) of the cranium of an adult Hyosciurus heinrichi showing limits of cranial and dental measurements. Abbreviations are explained in the text.

Fig. 2

The Conibear (single spring #110) body-gripping trap, which was used by Musser to catch nearly all the squirrels he collected. These traps were baited with a mixture of peanut butter, raisins, oatmeal, and bacon, and set on tree trunks and limbs spanning streams and ravines, in the crowns of understory trees and on large woody vines, on top of rotting tree trunks and limbs lying on the forest floor, and in runways beneath tree trunks and decaying treefalls. Photographed by Darrin P. Lunde.

Musser measured the skulls in most samples that are documented in this report. Nearly as many additional specimens were examined by him but the skulls are damaged and were not measured. Except for the specimens Musser collected, which were obtained mostly with Conibear traps (fig. 2), Sulawesi squirrels were collected by shooting with a shotgun and the pellets damaged many skulls, especially those from the small-bodied species, Prosciurillus murinus and P. abstrusus. Sometimes a full set of measurements, which was required for multivariate analyses of the cranial and dental variables we used, could be obtained from a damaged skull, but unfortunately most of the damaged skulls were unsuitable for our purposes.

Fig. 3

The northern portion of Sulawesi's central core showing the two regions where Musser worked, the Danau Lindu (left dashed square) and Malakosa (right dashed square) areas. Three of H.C. Raven's sites where he collected squirrels are also on the map: Gunung Lehio, southwest of Kulawi; Pinedapa, west of Mapane; Rano Rano, in the mountains west of Pinedapa. Enlargement of the Danau Lindu area is shown in figure 4 on the opposite page. Figure 17 shows an enlargement of the Malakosa area.

Musser also measured skulls of type specimens at the AMNH and USNM. However, we depended on the unselfish efforts of curators in several European and Asian museums for measurements of types held in those institutions.

Age and Sex

We separated specimens into one of the following five age groups:

These roughly defined age groups are unequally represented among samples: old adults and juveniles are scarce, adults and young adults are most common. Old adults, adults, and young adults were combined into samples from which measurements were obtained for multivariate analyses and univariate descriptive statistics.

Males and females were not separated in any of the statistical analyses. Inquiry into this aspect of morphological variation within and among species will have to be the subject of future studies.

Statistical Analyses

Standard univariate descriptive statistics (mean, standard deviation, and observed range) were calculated for the population samples (identified in table 1) and species listed in the tables.

TABLE 1

Population Samples from Species of Rubrisciurus, Hyosciurus, and Prosciurillus Employed in Analyses of Cranial and Dental Variables (Specimens measured are identified in footnotes. Localities, along with elevations and geographic coordinates, can be located in the gazetteers and on the distribution maps. Numbers in parentheses for each species indicate total number of specimens measured.)

Cluster analyses provided visual patterns that reflect similarity or contrast in the combination of cranial and dental dimensions among geographic samples of a single species or between samples of two different species. Measurements from complete skulls of adults only (young to old) were used in the analyses (geographic sources of the population samples, and identities of the specimens measured, are listed in table 1). All measurements were transformed to natural logarithms. Principal-components analyses were computed using the combination of cranial and dental variables indicated in various tables throughout the text. Principal components were extracted from a covariance matrix and projected on three axes, but usually significant structure was revealed only in the ordination of first and second principal-components factors, which are illustrated. (The pattern of specimen scores in plots employing first and third principal components were usually similar to those bounded by first and second axes.) SYSTAT 11 for Windows (2004 edition) was used for all analytical procedures.

Stomach Contents

Musser recorded in his field journal the contents found in stomachs of some freshly caught squirrels. Sometimes only a general description was possible—presence of fruit, seeds, arthropods, for example—but often freshly ingested and masticated fruit and seeds could be easily identified by color, shape, and texture as coming from particular trees or vines, and some arthropod remains could be identified to order. Many samples were preserved in ethanol and examined later in the laboratory using a dissecting microscope, which revealed the presence of additional particulates—termites especially—not seen in the field. We supplemented this material by extracting stomachs from undissected squirrels. Stomachs were removed by severing the posterior end of the esophagus and the anterior section of the duodenum. We bisected the isolated stomach along the midfrontal plane, transferred the contents to a white ceramic dish, and examined them with a dissecting microscope. In addition to remains of ingested foods, stomachs contained strands of hair, likely ingested during grooming, and sometimes nematodes. Stomachs emptied in the field are still attached to the gasterointestinal tract of carcasses preserved in fluid at AMNH. Those stomachs extracted in the laboratory are stored, with their contents, in leak-proof vials in the fluid collection at AMNH.

Our survey of stomach contents is far from exhaustive. We did not extract the stomach of every specimen collected, and we did not attempt to identify every tiny insect fragment. We also had no way to determine if any of the tree squirrels included vascular fluids (tree sap or gum) in their diets. We did not detect pieces of fungal remains at the gross level, but this was not conclusive because we did not survey stomach contents for spores or other microscopic evidence of fungi. During his daily work in the forest, Musser looked for squirrel activity, especially squirrels foraging, but this effort was secondary to his primary research centering on an inventory of murid rodents. Unfortunately, squirrels—as opposed to rats and mice—did not usually enter cage-traps (only two animals were caught in these live-traps) so Musser could not supply captives with a range of different forest foods to determine what would be accepted or rejected. The sole exception is described in the account of Hyosciurus ileile.

The problem of identifying arthropod remains, particularly insects, found in squirrel stomachs was solved by tapping David Grimaldi's (AMNH) wide-ranging knowledge of insects in particular and arthropods in general. Several times he unselfishly diverted his own research efforts to examine vials containing a range of different arthropods and to provide us with identifications along with ecological insights relating to the animals. His determinations and exposition of habitat preferences provided explicit ecological contexts for the arthropods that usually coincided with Musser's observations of the squirrel's behavior in the forest, and their external and skeletal morphology in the laboratory. We also consulted various general publications covering insects, but found Grimaldi and Engel's (2005) “Evolution of the Insects” to be the most rewarding, not only for the information it contained in text and illustrations, but for the intellectual satisfaction we derived from learning about different insect groups of interest to us and their evolutionary origins.

Geography

The island of Sulawesi consists of a central core from which four arms or peninsulae radiate (see the distribution maps): the northern peninsula, which ends in a northeastern jog; the east-central peninsula; the southeastern peninsula; the southwestern peninsula. We use these informal labels when describing distributions of various species of squirrels over the island. Squirrels also occur in Kepulauan Sangihe, the archipelago north of the northeastern tip of Sulawesi's northern peninsula.

In the text and in some tables we refer to the west-central region or western mountain block, which forms the western portion of Sulawesi's central core. It is that region of foothills, peaks, and interior valleys situated above 100 m and lying roughly west of Danau Poso and extending from the Palu area in the north to Pegunungan Latimojong in the south. For our purposes here it excludes the coastal strip along the shores of the Makassar Strait simply because no nonvolant mammals have been collected there. A suite of mammals, from shrews to rats, have been collected only in the west-central region: a few species are found in tropical lowland evergreen rain forest covering lower altitudes on foothills and in valleys, but most occur at higher altitudes in montane forests.

Throughout the report we use the Indonesian terms sungai (stream or small river), kuala (stream discharging directly into the sea), gunung (mountain), pegunungan (mountain range), pulau (island), kepulauan (archipelago), selat (strait), tanjung (cape), and teluk (bay).

Musser's Transect

During 1973–1976, Musser lived and worked in the forests of central Sulawesi where he focused on an inventory of murid rodents along a transect extending from near sea level into montane habitats. While murids were of primary interest, other small mammals were also trapped, among them reasonable samples of Rubrisciurus rubriventer, three species of Prosciurillus, and the two species of Hyosciurus. These samples proved to be extremely important, in that habitat and other biological information are attached to specimens. Musser's experience with the squirrels where he worked provided ecological insights into habitats and distributions for species occurring in other geographic regions of Sulawesi. In parts of the text, we refer to “Musser's transect” and we provide three maps (figs. 2, 3, and 17) illustrating the location of camps along that transect. Detailed descriptions of the camps and forests will be produced elsewhere (Musser, ms), but we insert the maps here to give readers a visual orientation to the regions surveyed. Ambient air temperatures recorded at the various camps are summarized in table 2; we refer to these data in the descriptions and figures of habitats.

Fig. 4

The Danau Lindu area. Where the Sungai Oha Kecil flows into the Sungai Miu at 290 m was Musser's lowest camp along his transect; the summit of Gunung Nokilalaki was the highest place he worked. Tropical lowland evergreen rain forest embraces the area from the Sungai Oha Kecil to the camp along the Sungai Tokararu at 1150 m. The camp at 1440 m was on a ridge, Gunung Kanino, in lower montane rain forest. The lower camp at 1150 m was at the western end and base of the ridge. The highest camp at 1700 m was situated on the flanks of Gunung Nokilalaki, which at higher altitudes was covered with upper montane rain forest. Prosciurillus topapuensis and P. murinus occurred throughout the forests from the lower camps to Gunung Nokilalaki, Rubrisciurus rubriventer was encountered through much of the same altitudinal range but not higher than Gunung Kanino. Both species of Hyosciurus were trapped in the area, H. ileile in the lowlands and H. heinrichi on the mountain; the elevational ranges of each species abut at Gunung Kanino.

Fig. 5

Collection localities for samples of Rubrisciurus rubriventer. Numbers key to localities described in the gazetteer where specimens are also identified by museum initials and catalog numbers. The inset map, right (rectangle on larger map, above), contains collection sites (10–21) scattered along Musser's transect from the Sungai Oha Kecil to the slopes of Gunung Kanino. The dashed contour line at 1300 m marks the approximate boundary between tropical lowland evergreen rain forest and tropical lower montane forest.

TABLE 2

Minimum and Maximum Ambient Air Temperatures Recorded from Coastal Lowlands to the Summit of Gunung Nokilalaki in Central Sulawesi^a Temperatures are summarized by mean and ranges (in parentheses). Abbreviations: G  =  Gunung, S  =  Sungai, K  =  Kuala.

Gazetteers

Localities from which samples were collected, along with the institutional initials and catalog number of each specimen examined, are listed in the gazetteers scattered throughout the text in relevant accounts of species. Descriptions of localities and elevations (recorded in meters or feet, depending on the convention used by the collector) were taken from labels attached to skins. These basic data were enhanced where necessary by information from field journals, other archival material, and published expeditionary accounts and gazetteers; sources are cited in the locality entry.

Spelling of locality names are those approved by the United States Board on Geographic Names in the Gazetteer of Indonesia, Third Edition, volumes 1 and 2, published by the Defense Mapping Agency, Washington, D.C. in 1982 (referenced as USBGN, 1982). Some places could not be located in that gazetteer but were found on the topographic map sheets described below; alternate spellings of some place names come from Musser's field journals and older maps.

Coordinates for some collection localities were found in USBGN (1982) or the Gazetteer of Celebes published in 1944 through the Hydrographic Office of the United States Navy Department (HOUSND, 1944). Coordinates for most of H.C. Raven's collection localities were estimated from his personal copy of a Dutch map of Celebes on which he had marked his camp sites and travel routes (Overzichtskaart van het eiland Celebes, Schaal 1∶1,250,000, “met aanduiding van de politieke indeeling, de organisatie van het bestuur, de bestaande en nog aan te leggen verkeerswegen en van de groote cultuur-en industrieele centra.” Samengesteld op last van de N. I. Regeering. Published in 1909), and referred to in the text as “Raven's map.” Coordinates for Musser's collection localities, as well as height above sea level for places for which elevations were not recorded by other collectors, were estimated from “JOINT OPERATIONS GRAPHIC-GROUND” topographic maps, scale 1∶250,000, compiled by Mapping and Charting Establishment RE, 1969, and published by the Director of Military Survey, Ministry of Defence, United Kingdom, 1970, or by the Army Map Service, Washington, D.C. (Sheets NA 51-9 [1967], NA 51-12 [1967], NA 51-14 [1967], SA 50-8 [1971], SA 51-1 [1970], SA 51-5 [1967], and SA 51-14 [1967], SB 50-8 [1966], SB 51-1 [1970]). Gunung Topapu, the type locality for Prosciurillus topapuensis, was located by Thomas von Rintelen on an old map in the Berlin Museum that had been used by Paul and Fritz Sarasin, collectors of the holotype; a copy of the map was sent to Musser.

Forests

The tropical rain forests embracing the habitats of Sulawesi's endemic squirrel species will be described broadly by applying three of the forest formations categorized by Whitmore (1984): tropical lowland evergreen rain forest, tropical lower montane rain forest, and tropical upper montane rain forest. Whitmore's descriptions are very good and, as he notes, an extension and elaboration of P.W. Richards' (1952) classical “The Tropical Rain Forest,” which readers will also find informative (a second edition was published in1996).

Institutions

Specimens examined and referred to in this report are deposited in the collections of the American Museum of Natural History, New York (AMNH); the Natural History Museum, London (BMNH); Lance A. Durden (LAD), the Museum Zoologicum Bogoriense, Cibinong, Java (MZB); and the National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM). Holotypes of all new species of lice described in this paper are deposited in the USNM.

Specimens, Procedures, and Abbreviations

Host squirrels were collected by W.J.C. Frost, I.A. Hanski, G. Heinrich, G.G. Musser, or H.C. Raven. Lice were removed from squirrel pelts by L.A. Durden. Description of the new species of lice presented in this paper follows the format and terminology of Kim (1966), Kim and Ludwig (1978), and Durden and Musser (1991, 1992). Drawings of entire lice conventionally illustrate dorsal structure to the left of the midline and ventral features to the right. Measurements were made using a calibrated micrometer inserted into the eyepiece of a high-power phase-contrast microscope. Only adult lice of the eight new species of Anoplura are described; a few immatures were collected for three of the new species but sample sizes were too small for reliable analyses. For two of the eight new species, only female lice were available; these two species were therefore excluded from the phylogenetic analysis.

Abbreviations for anatomical structures used in the descriptive portions of this work are as follows:

Phylogenetic Analysis of Lice

Phylogenetic analyses of 43 morphological characters for 14 taxa were performed using maximum parsimony (MP) and Bayesian approaches. PAUP*4.0b10 (Swofford, 2003) was used to perform equally weighted MP searches with 10,000 random addition replicates and tree bisection-reconnection (TBR) branch swapping. All characters were treated as unordered. To assess nodal support, nonparametric bootstrap analyses (Felsenstein, 1985) and computation of Bremer support indices (Bremer, 1988, 1994) were performed. Bootstrap analyses of equally weighted data were performed with 1000 pseudoreplicates and 10 random sequence additions per replicate using TBR branch swapping. Bremer support values were calculated using the program TreeRot v. 3 (Sorenson and Franzosa, 2007) using PAUP* (TBR branch swapping, 100 random addition sequences per calculation).

Bayesian phylogenetic analyses were performed using MrBayes 3.1.2 (Ronquist and Huelsenbeck, 2003). Morphological characters were treated as standard and analyses were performed using the Mk model with a gamma distribution (Lewis, 2001). Bayesian analyses were initiated with random starting trees, run for 10 million generations with four incrementally heated chains (Metropolis-coupled Markov chain Monte Carlo; Huelsenbeck and Ronquist, 2001), and sampled at intervals of 1000 generations. To avoid entrapment on local optima, two independent Bayesian analyses were run and log-likelihood scores were compared for convergence (Huelsenbeck and Bollback, 2001; Leaché and Reeder, 2002). Log-likelihood scores of sample points were plotted against generation time to assess stationarity and all burn-in points (the first 2000 trees) were discarded. The retained equilibrium samples were used to generate a 50% majority rule consensus tree with the percentage of samples recovering any particular clade representing that clade's posterior probability.

Host and parasite trees were assessed for similarity using a tree-based method to consider similarities between trees as possible instances of codivergence. Tree-based methods compare only the branching structure of host and parasite trees to determine if more codivergence events are present than would be observed by chance. The host tree was compiled from the literature (Mercer and Roth, 2003). However, because of the polytomy among the three species of Prosciurillus, three different analyses were performed, each using a different combination of two of the three host species (P. abstrusus and P. leucomus, P. abstrusus and P. murinus, and P. leucomus and P. murinus) and their respective lice.

Reconciliation analysis (TreeMap 2.0β; Page, 1994; Charleston, 1998; Charleston and Page, 2002) was used to test for phylogenetic congruence between host and parasite trees. TreeMap 2.0β finds the least costly reconstruction of host-parasite relationships while maximizing the number of cospeciation events. The default settings of TreeMap were used (assigning a cost of zero for cospeciation events and a cost of 1 for host switches, losses, and duplications). The parasite tree was randomized 100 times and the observed number of cospeciation events was compared to the resulting null distribution of cospeciation events to determine whether the number of cospeciation events recovered from the reconciliation analysis was significant.

Our formal introduction to Sulawesi's endemic sciurid fauna begins with the following section reviewing the current classification of living squirrels.

Gazetteer and Specimens Examined

Collection localities for the 92 specimens of R. rubriventer studied are listed below. The number preceding each locality keys to a symbol on the map in figure 5.

Fig. 6

Views of skull and dentary of an adult male Rubrisciurus rubriventer (AMNH 226053) from Kuala Navusu (30 m) in the central core of Sulawesi. Occipitonasal length  =  67.4 mm.

Fig. 7

Specimen scores representing five population samples of Rubrisciurus rubriventer projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples are: filled triangle  =  northeastern peninsula (Rurukan, Temboan; N  =  2); star  =  northern peninsula (Bumbulan, Ile-Ile; N  =  5); filled circle  =  north-central region1 (Sungai Oha Kecil, Sungai Miu, Sungai Sadaunta, Tomado, Gunung Kanino, Kulawi; N  =  18); asterisk  =  north-region 2 (Kuala Navusu, Sungai Tolewonu; N  =  19); filled square  =  southeastern peninsula (Wawo, Masembo, Tanke Salokko; N  =  5). The score located farthest to the right in the ordination represents AMNH 224623, an especially large adult from Sungai Oha Kecil. Delicate arrows identify scores of four specimens from Gunung Kanino collected in lower montane forest, 1274–1418 m. Lettered arrows indicate scores for the specimen from Wawo (w) collected on the coastal plain at 50 m in tropical lowland evergreen rain forest and the squirrel from the inland mountains at Tanke Salokko (t) at 1400 m taken in lower montane forest; both places are in the southeastern peninsula of Sulawesi. See table 9 for correlations and percent variance.

1. Manado (also spelled “Menado”), 01°30′N, 124°50′E, coastal plain near sea level: RMNH specimens “d–g” in Jentink's (1888: 23) catalog; ZMA 15.933, 19.832, 19.833.

2. Rurukan, 01°21′N, 124°52′E: AMNH 196509 (500 m), 101324 (1000 m).

3. Gunung Masarang, 01°19′N, 124°51′E, 3500 ft (1067 m): BMNH 97.1.2.14.

4. Temboan, on Kuala Kalait, “a new clearing of eight houses and lies from Mt. Sapoetan south, 55° west and about six miles from Loboe,” wrote Raven in his field journal, 1916: 3 (in Mammal Division Library at USNM), 01°03′N, 124°33′E (estimated from Raven's map), 500 m (estimated from Sheet NA 51-12): USNM 217824, 217905.

5. Tomohon, 01°19′N, 124°49′E, 700–800 m (estimated from Sheet NA 51-12): BMNH 99.10.1.7; NMB 3329, 1201/9538. Meyer (1899: 22) reported specimens from here.

6. Tulabolo (“Toelabello” in Jentink's catalog, 1888: 23), 00°31′N, 123°16′E, 760 ft (230 m; see Fooden, 1969: 137, for details): RMNH: specimen “c” in Jentink's (1888: 23) catalog. “Modélido,” someplace in the Tulabolo-Gorontalo area east of Bumbulan: RMNH: specimen “b” in Jentink's (1888: 23) catalog.

7. Bumbulan, 00°29′N, 122°04′E, coastal plain near sea level: AMNH 153909–11, 153279; MZB 6257.

8. Gunung Ile-Ile, 00°58′N, 121°48′E, 500 m: AMNH 101321–23, 196508.

9. Valley of Sungai Miu, Sungai Oha Kecil (small tributary on left side of Sungai Miu), 01°22′S, 119°57′E (near confluence with Sungai Miu; estimated from Sheet SA 50-8), 290 m: AMNH 224621, 224622.

10. Sungai Oha Kecil, 1300 ft (396 m): AMNH 224623.

11. Valley of Sungai Miu, Sungai Miu (right side), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 350 m: AMNH 224055, 224056.

12. Valley of Sungai Miu, Sungai Sadaunta (also spelled “Sidaonta” or “Sidaunta”; tributary on right side of Sungai Miu), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 675 m: AMNH 224052–054.

13. Sungai Sadaunta: 2500 ft (762 m), AMNH 224624; 2550 ft (777 m), AMNH 224629; 2600 ft (793 m), AMNH 224625.

14. Sungai Sadaunta: 2700 ft (823 m), AMNH 224626.

15. Sungai Sadaunta: 3050 ft (930 m), AMNH 224628, 226839, 226840.

16. Sungai Sadaunta, 3300 ft (1006 m): AMNH 224627.

17. Valley of Danau Lindu, Tomado (a village on western shore of Danau Lindu), 01°19′S, 120°03′E (estimated from Sheet SA 5-8), 1000 m: AMNH 223023–025, 223466, 223467, 224057; USNM 218711.

18. Gunung Kanino, 01°17′S, 120°08′E (estimated from Sheet SA 50-8), 4180 ft (1274 m): AMNH 223552.

19. Gunung Kanino, 4600 ft (1402 m), AMNH 225488; 4650 ft (1418 m), AMNH 225489, 225490.

20. Gunung Kanino, 4960 ft (1512 m): AMNH 225491.

21. Malakosa, Kuala Navusu, 00°58′S, 120°27′E (estimated from Sheet SA 51-1): 100 ft (30 m), AMNH 226052–054; 130 ft (40 m), AMNH 226055, 226056; 150 ft (46 m), AMNH 226058; 200 ft (61 m), AMNH 226057; 400 ft (122 m), AMNH 226059; 500 ft (152 m), AMNH 226060, 226061; 800 ft (244 m), AMNH 226062.

22. Tolai, Sungai Tolewonu, 01°04′S, 120°27′E (estimated from Sheet SA 50- 8): 500 ft (152 m), AMNH 226526, 226528–31; 540 (165 m), AMNH 226527; 550 ft (168 m), AMNH 226532; 750 ft (229 m), AMNH 226533; 850 ft (259 m), AMNH 226534; 1000 ft (305 m), AMNH 226535.

23. Kulawi, 01°27′S, 119°59′E, 500 m: USNM 218710.

24. Besoa, 01°44′S, 120°13′E (for “Besoa District,” HOUSND, 1944): USNM 219522. H.C. Raven, who collected the squirrel in 1917, noted that “Besoa is a large level plain, undoubtedly a former lake bed, surrounded by mountains, which are covered by heavy forests; the tops of most of the mountains are above 2000 meters, the level plain is said to be about 1300 meters, or perhaps more. The plain is perhaps 2 or 3 miles wide by about 3 miles long and most of the area is covered with several varieties of long coarse grasses and reeds; in several places there are wet rice fields and the natives have made a few clearings on the lower slopes of the mountains. In some places the lower slopes are covered with grass” (Riley, 1924: 3). Raven collected animals from at least two places in the Besoa region (Doda and Gunung Taewo). No elevation or precise provenance is associated with USNM 219522.

25. Pegunungan Quarles, Bulu (Gunung) Karua (referred to as “Rantekaroa, Quarles Mt.” on specimen tags), 02°56′S, 119°39′E, 4000 ft (1220 m): BMNH 40.674.

26. Palopo, 03°00′S, 120°12′E, coastal plain near sea level: MZB 6258–60.

27. Wawo, on the plain between the coast and western foothills of Pegunungan Mekongga (also spelled “Mengkoka”), 03°41′S, 121°02′E, 50 m: AMNH 101314–16.

28. Pegunungan Mekongga (also spelled “Mengkoka”), Tanke Salokko (the highest spot in Pegunungan Mekongga; see the maps and discussion in Heinrich [1932] and Stresemann [1940]), 03°35′S, 121°15′E (for the Pegunungan): 600 m, AMNH 101313; 1400 m, AMNH 101312.

29. Pegunungan Mekongga, Masembo, which is southeast of Wawo and the highest place in the southern portion of Pegunungan Mekongga (see maps and discussion in Heinrich [1932] and Stresemann [1940]), 03°35′S, 121°15′E (for the Pegunungan), 550 m: AMNH 101317–19.

30. Lalolei (spelled “Lalolis” on specimen tags and some maps), 03°57′S, 122°03′E, 300 m: AMNH 101320.

31. Lamoncong (“Lamontjong” is the older spelling), in the upper part of the Walanae River Valley, approximately 05°S, 119°50′E (see map in Mulvaney and Soejono, 1970: 164, and Bulbeck, 1996: 1014), 300–600 m: subfossil fragment of a skull described by Sarasin (1905: 47) from a limestone cave. We have not seen this specimen, but Sarasin described what can only be an example of Rubrisciurus, and he identified it as “Sciurus rubriventer Müll. Schl.?”

The following specimens were studied but the places where they were caught have not been mapped.

A. “Célèbes” (see Jentink, 1888): RMNH 13341 (specimen “a” in Jentink's [1888: 23] catalog; holotype of Sciurus rubriventer); see account of type locality. “Celebes”: BMNH 40.675, 43.238.

B. Central Core, Tamalanti: BMNH 40.691a. Laurie and Hill (1954: 156) noted that Tamalanti is a “Plantation between Rantekaroa [02°50′S, 119°50′E] and Koelawi [01°27′S, 119°59′E],” which was also the only information Musser and Paula Jenkins found when they searched through fieldnotes and other documents at BMNH. No elevation is provided for the specimen, but most collections from Tamalanti came from 3300–3800 ft (1006–1159 m) according to Paula Jenkins (personal commun.).

C. “Tannya”: FMNH 8328. We could not locate this place.

Rubrisciurus rubriventer (Müller and Schlegel, 1844)

Sciurus rubriventer Müller and Schlegel, 1844: 86.

Holotype and Type Locality

The holotype of Rubrisciurus rubriventer is an adult male (RMNH 13341, specimen “a” in Jentink's [1888: 23] catalog) obtained by E.A. Forsten sometime during 1840–1842. It consists of a skin mounted in a live position; no skull is present. The skin apparently was in bad condition when prepared; most fur on the abdomen, right flank, caudal part of the left flank, and part of the left thigh is missing.

The type locality is “Célèbes,” as listed in Jentink's (1888: 23) catalog. Forsten obtained most of his material in the region near the tip of the northeastern peninsula, which is in the administrative district of Minahasa (Kabupaten Minahasa), between 1° and 2° north latitude, Propinsi Sulawesi Utara, Indonesia. Laurie and Hill (1954: 94) indicated “Minahasa, north Celebes” to be the type locality, which restricted the location to that political unit. However, the type locality should rather be defined as “NE Celebes” ( =  NE Sulawesi) because Forsten also worked in the area of Gorontalo and as far west as Paguat (September–November 1841; see Van Steenis-Kruseman [1950: 179] and Forsten's unpublished diary in the archives of the Leiden Museum); hence, it cannot be excluded that specimens from that area are among Forsten's material (C. Smeenk, in litt., 2008). For additional information covering Forsten's travels in northeastern Sulawesi, see the account of Prosciurillus leucomus.

Emended Diagnosis

Rubrisciurus is monotypic so the emended generic diagnosis applies to the species, R. rubriventer.

Geographic and Altitudinal Distributions

Voucher specimens reflect a distribution throughout most of the mainland of Sulawesi; no material has been collected from offshore islands (see gazetteer and map in figure 5). Most collection records are in regions that are or were covered with primary tropical lowland evergreen rain forest. A few samples come from mountains at altitudes where tropical lower montane rain forest dominates (Gunung Kanino in the central core, and Pegunungan Mekongga on the southeast peninsula). No specimens have been collected from high elevations in cool and wet upper montane rain forest.

Provenances for modern specimens cover most of Sulawesi; only the east-central peninsular extension of the central core, which has not been surveyed for small mammals in any adequate endeavor, and the southwestern peninsula lack modern records. Unfortunately, except for some forested limestone tracts and higher slopes of the volcano Gunung Lompobatang, the southwestern peninsula has mostly been deforested; the former forest cover has been converted to farms and tree plantations from about 1700 m to the coastal lowlands (Fraser and Henson, 1996; see the map showing remaining forest tracts in Froehlich and Supriatna, 1996; and map 8d in MacKinnon, 1997). But, Rubrisciurus did occur there in prehistoric times as documented by a subfossil cranial fragment excavated from a rockshelter at Lamoncong, in the southern part of the peninsula northeast of Ujung Pandang (Sarasin, 1905). Archaeological artifacts from Sulawesi rockshelters are usually associated with the period of Toalean prehistory, 7000–5500 years B.P. (see references in Bulbeck, 1996). There are numerous prehistoric cave sites in the southern peninsula (Bulbeck, 1996) but, with the exception of the Lamoncong site, remains of Rubrisciurus have not been identified in the large samples of subfossil material excavated from some of them (as determined by Musser's study of subfossil cranial and dental remains).

In most other surveyed geographic regions of Sulawesi, Rubrisciurus rubriventer occurs with a member of the Prosciurillus leucomus group, with P. murinus, and with the two species of ground squirrels, Hyosciurus ileile and H. heinrichi (table 6). Hyosciurus has not been recorded from the southwestern peninsula. A member of the P. leucomus group is represented by a subfossil fragment from a cave deposit in the region (see account of Prosciurillus sp.). Modern samples of P. murinus have been collected from the southwestern peninsula but only above 1100 m on foothills and higher slopes of Gunung Lompobatang (see gazetteer), which is still clothed by some forest: the upper forested slopes of the volcano form an island “in a sea of densely-populated agricultural land east of Ujung Pandang” (Whitten et al., 1987: 519). So all three species of tree squirrels are now represented by subfossil or modern specimens from the southwestern arm. Murid rodents (rats) occurring with Rubrisciurus in lowland and lower montane forest formations in other geographic regions of Sulawesi (Taeromys celebensis, Taeromys punicans, Bunomys chrysocomus, Bunomys andrewsi, Rattus hoffmanni, and Paruromys dominator are examples) either live on the southwestern peninsula now or did in the past (Musser, 1984).

Elevational distributions gleaned from collection data tied to voucher specimens (see gazetteer) for three regions of Sulawesi are summarized here. On the northern peninsula, records extend from the coastal plain to 1067 m on Gunung Masarang. All places are within the elevational distribution of tropical lowland evergreen rainforest habitats. Specimens obtained in the central core of the island bracket habitats from the coastal plain at 30 m (Kuala Navusu) to those in the mountains (Gunung Kanino at 1512 m), and range from tropical lowland evergreen rain forest to tropical lower montane rain forest; Musser did not trap or see R. rubriventer in the forests above approximately 1500 m. Lower montane forest at 1400 m on Tanke Salokko in Pengunungan Mekongga is the highest collection record for R. rubriventer on the southeastern peninsula of Sulawesi; all other records lie within 50 to 500 m in tropical lowland evergreen rainforest environments.

Description

The original description of rubriventer (as a species of Sciurus) by Müller and Schlegel (1844: 86) is short (translated from the original in Dutch by Chris Smeenk [in litt., 2008]; the Dutch text is reproduced in appendix 2):

Rubrisciurus rubriventer is the largest-bodied of the species of tree squirrels endemic to Sulawesi (length of head and body, 250–305 mm; length of hind foot, 67–77 mm; weight, 500–860 g; see tables 2, 7) and one of the largest of the tree squirrels and ground squirrels that are native to the Indomalayan region. It is exceeded in body size only by species of Ratufa (weight  =  875–1620 g for Malayan and Bornean R. bicolor and R. affinis; see Medway, 1969: 56, and Payne et al., 1985: 233) and the Bornean endemic, Rheithrosciurus macrotis (weight  =  1170–1280 g; see Payne et al., 1985: 243).

TABLE 7

Descriptive Statistics for Measurements (mm) of Lengths of Head and Body, Tail, Hind Foot, and Ear, and for Weight (g), Derived from Samples of Rubrisciurus rubriventer^a Mean ± 1 SD, observed range (in parentheses) and size of sample are listed. Mean values were used to compute LT/LHB. Specimens measured are listed below.^b

The color pattern, resplendent in its richly pigmented red and orange hues, of the large-bodied and long-legged R. rubrisciurus is best described this way: a reddish brown tail; reddish underparts, forelegs and feet, shoulders, thighs, hind legs and feet; brownish head and back speckled by buff, orange and black; ears highlighted by prominent glossy black tufts. The short fur (6–8 mm thick) covering the entire underparts, from chin to base of tail, is a rich, bright, reddish orange, which darkens to reddish maroon over dorsal surfaces of the front legs and feet, shoulders, along sides of the body and thighs, and dorsal surfaces of hind legs and feet. The top and sides of the head, and rest of the dorsum from the head to base of the tail, are covered by a thick (15–20 mm), rich brown coat flecked with buff, orange, and black (a combination provided by the overhairs with dark gray bases, subterminal buff or orange bands, and black tips, along with black guard hairs). There is a dark crescent above each eye, and the eye is circled by a wide buffy ring. The ears conspicuously contrast with the head, neck, back, and rump because the medial surface of each pinna is covered by soft black hairs that converge to form a tuft 5–10 mm long projecting beyond the contour of the dorsal pinna margin, and rimming the posterior margin (top and back edges of the pinna are defined by the black hairs, but the long tuft is confined to the dorsal margin). Color and extent of this tufting is closely similar to that present in P. leucomus. The tail of R. rubriventer is shorter than length of the head and body (LT/LHB  =  82%), both dorsal and ventral surfaces are dark reddish brown (approaching maroon in some individuals), without the darker or paler borders formed by distal banding patterns of the hairs that are common to species of Prosciurillus.

The juvenile coat exhibits a color pattern similar to that of adults but the fur is thinner (hairs are finer), shorter, and the coloration typically duller, the red tones muted instead of being rich and bright.

Females have four teats arranged in two inguinal pairs. A single embryo was found in each of the few females of Rubrisciurus rubriventer caught by Musser.

Views of the large, stocky skull of R. rubriventer are illustrated in figure 6. Note the robust and relatively long rostrum, prominent anterior projection of the zygomatic root concealing the anterior opening of the infraorbital canal, high dorsal process of the jugal component of the zygoma, short orbit, position of the postorbital process well in front of the anterior margin of the braincase, prominent temporal ridges that unite to form a strong sagittal crest, posterior margin of the bony palate situated anterior to the backs of the parallel tooth rows, proodont (procumbent) upper incisors, wide fourth premolar and molars, and sturdy dentary with its high ramus.

Fig. 8

Habitat of Rubrisciurus rubriventer in tropical lowland evergreen rain forest at Kuala Navusu, 150 m. Two other species of tree squirrels live in the same forests: Prosciurillus alstoni prefers the upper canopy layer, and P. murinus forages through the understory trees. All three species were caught in traps set on top of tree trunks bridging streams, much like the trunk lying across the stream in the photograph. See table 2 for range of ambient temperatures recorded during the trapping period. Photographed in 1975.

Another trait bears inspection. At each posterolateral margin of the bony palate just caudal and slightly medial to the end of the tooth row is a large notch or enclosed foramen (the posterior maxillary notch or foramen) that transmits the descending palatine vein (Wahlert, 1974). The vein passes through a notch in most specimens of R. rubriventer (ends of the notch are connected by cartilage, which is usually removed when the skull is cleaned), which is also typical in all the species of Prosciurillus. In a few examples of R. rubriventer, the opening is enclosed by bone forming a foramen (as shown in fig. 6), which is the typical configuration in both species of Hyosciurus.

Some of the other cranial traits seen in R. rubriventer are common to species of Prosciurillus, Hyosciurus, and most, but not all, other sciurids. Some examples are the proximal borders of the nasals, which lie anterior to the bordering premaxillary-maxillary sutures; moderate to prominent postorbital processes of the frontals; posterior border of the ventral zygomatic root at about the level of the second upper premolar; short and typically narrow incisive foramina contained entirely in the premaxillaries; a bony palate with a smooth ventral surface and penetrated by small postpalatal foramina at about the level of the second upper molars; wide mesopterygoid fossa relative to skull size, its roof entirely osseous or showing slitlike sphenopalatine vacuities; relatively narrow pterygoid fossae bounded by a high lateral ridge; well developed hamular processes; moderately large ectotympanic bullae tightly attached to the basicranium; spacious postglenoid foramen just dorsad of the ectotympanic capsule; moderate-size coronoid process relative to overall outline of the dentary, large condyloid and angular processes, and deeply concave posterior border of the dentary.

Cranial and dental measurements for the population samples of R. rubriventer are summarized in table 8.

TABLE 8

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Separate Population Samples of Rubrisciurus rubriventer Mean ± 1 SD and observed range (in parentheses) are listed.

Comparisons

Members of the Prosciurillus leucomus and P. murinus groups as well as the species of Hyosciurus are all much smaller in body size than is Rubrisciurus rubriventer (table 3), none displays its bold and bright reddish, orange, brownish, and black patterning, and all females show three pairs of teats (see the appropriate accounts of species).

Geographic Variation

No additional scientific names have been attached to geographic samples of R. rubriventer, most likely a reflection of its generally uniform attributes associated with body size, pelage coloration and patterning, and cranial and dental dimensions among samples from the northern peninsula of Sulawesi, its central core, and southeastern arm. Sody (1949: 108) came close to naming a subspecies when he discussed the samples at MZB that he studied: a single specimen from Bumbulan on the northern peninsula and three from Palopo in the southern sector of the central core of Sulawesi (see gazetteer and fig. 5). Sody wrote that,

Musser examined all four squirrels. The color contrast noted by Sody reflects primarily biological age of the specimens. The squirrel from Bumbulan is an adult covered in a full, richly pigmented adult coat. Of the three from Palopo, two are young and were captured as they were molting from juvenile into adult pelage, and the third is a juvenile completely covered in juvenile fur. Juveniles have thinner and shorter pelage showing slightly duller reddish hues along sides of the body, and duller fur over the head and back (the “mixture of brownish and buff”) in some individuals, a conspicuous contrast with the thicker adult coat with its brilliant, darker hues.

Even among adults within a single geographic sample, or even in a sample from the same collection site, the fur over the head and back varies in color intensity among individuals. Some squirrels show a dark background speckled with buff (the buffy bands of the hairs are narrow, the black bands wider), but others have brighter fur in which the buffy speckling predominates (the buffy bands are wider, the black narrower); the brilliant reddish hues of the appendages, shoulders and thighs, and underparts are constant within and among population samples. Wear is also reflected in samples. Some older adults with worn pelage have darker upperparts because the fur has worn past the buffy or ochraceous distal bands and the remaining black bands of the hairs provide the prevalent tone.

All samples of R. rubriventer, from wherever they were collected on Sulawesi, exhibit similar pelage coloration and patterning over the body, whether adults or juveniles.

The possible difference in measurements suggested by Sody (1949: 108) can also be attributed to age. The adult from Bumbulan has a larger skull (greatest length  =  68.5 mm) compared with the smaller skulls of the three younger squirrels from Palopo (greatest lengths are 64.0, 64.6, and 65.3 mm). The length of the skull of the Bumbulan animal falls within the range of variation we record within each of our geographic samples (see ONL in table 8). That measurement compatibility reflects the general geographic uniformity of coat color and pattern among our samples of adult squirrels as well as overall size of skull and length of maxillary tooth rows. This cranial and dental dimensional variation within and among geographic samples is summarized in figure 7 where specimen scores representing five population samples of R. rubriventer (identified in table 1) are projected onto the first and second principal components extracted from principal-components analysis. The spread of scores along the first axis is primarily influenced by size, the larger and generally older adults spreading to the right, the smaller and usually younger adults towards the left. Covariation in most cranial variables—particularly length and breadth of rostrum, length of nasals, and lengths of diastema and bony palate—are the most influential in pushing scores along the first principal component; zygomatic breadth, mastoid breadth, and length of maxillary tooth row (PM4–M3) provide negligible impact (table 9).

Fig. 9

Reproduction of Meyer's (1896) color plate showing “Sciurus leucomus” ( =  Prosciurillus leucomus) at the top, “Sciurus tonkeanus” ( =  Prosciurillus alstoni) in the center, “Sciurus rosenbergii” ( =  Prosciurillus rosenbergii) on the bottom right and “Sciurus tingahi” (also  =  Prosciurillus rosenbergii) at bottom left.

TABLE 9

Results of Principal-Components Analysis Contrasting Population Samples of Rubrisciurus rubriventer Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 7.

No significant variation among measured cranial and dental dimensions that reflects altitudinal variation, particularly between lowland tropical evergreen rainforest habitats and lower montane forest, is apparent among our samples. Two sets of specimens provide examples. Scores shown in figure 7 representing specimens collected along Musser's transect in the central core of Sulawesi from Sungai Oha Kecil at 290 m to Gunung Kanino at 1418 m are identified by filled circles; slim arrows point to scores for the four squirrels collected in lower montane forest between 1274 and 1418 m on Gunung Kanino. Not only do most congregate within the cloud of points representing specimens from tropical lowland evergreen rain forest between Sungai Oha Kecil at 290 m and Tomado at 1000 m, but also within lowland samples from Kuala Navusu and Sungai Tolewonu (30–305 m; identified by asterisks) to the east of Gunung Kanino, and Masembo at 550 m (filled squares) in the southeastern peninsula. The other set originates from the southeastern peninsula and their specimen scores are indicated by filled squares. The square identified as Wawo at 50 m in tropical lowland evergreen rain forest rests next to the square for the specimen from Tanke Salokko at 1400 m in lower montane forest.

No discrete clouds of scores are present in the principal-components ordination that represents separate geographic regions. There are no unique constellations, for example, identifying samples from the northern peninsula, from the central core, or from the southeastern peninsula; all points derived from geographic samples are intermixed. Because each large sample ranges in age from young adults to old adults and includes males and females, the distribution of scores is also a reflection of age, possibly secondary sexual variation, and individual variation within an age class that is unrelated to age.

Four points at the right margin of the cloud in figure 7 require discussion. AMNH 224623, which is an especially large adult from Sungai Oha Kecil, is responsible for the score located farthest to the right in the ordination; most scores for other individuals from that collection site are nested within the primary cloud. Just to the left of AMNH 224623 is another point for a large adult from Sungai Oha Kecil, and that score is aligned with two scores identifying our only measured skulls from the northeastern limb of the northern peninsula. These two are also large adults, but we do not know if they are typical of the population in the northeast. We record more than a dozen specimens from that region (see gazetteer) but some are juveniles, some consist only of skins, and others have damaged skulls. A larger sample of adults with intact skulls needs to be studied to assess the range of cranial and dental morphometric variation within the northeastern peninsular population.

Our analysis of geographic variation in cranial and dental dimensions among samples available to us is rough. The results presented here should be tested by comparing larger samples of comparable age, supplemented by molecular data. What we convey here is the absence of significant differences in color pattern of the pelage, along with cranial and dental dimensions, among available samples of R. rubriventer from the different major geographic regions of Sulawesi. This large red squirrel looks the same wherever it is encountered on Sulawesi, a startling contrast to the variation associated with fur color and patterns among geographic samples of the Prosciurillus leucomus complex (see those accounts).

Ecology

Rubrisciurus rubriventer is diurnal, arboreal, and terrestrial. It nests in the forest understory and forages in the understory canopy and on the ground; Musser never saw any in the canopy layer or higher in the crowns of emergent trees. When squirrels were encountered, they were traveling through crowns forming the understory canopy or along the ground. Of the two squirrels briefly seen by Durden in the northeastern peninsula, one was in an understory tree and the other was on the ground. Musser trapped all his specimens on rotting tree trunks (“boles” to the botanists) lying on the forest floor, on tree or palm trunks lying across streams, on limbs of understory trees, and on the ground in scrub adjacent to tall forest (see summary of habitats at trapping sites in table 10, and the forest in fig. 8). Except for the specimen trapped in scrub, which was near tall forest, all sightings and trapping records of R. rubriventer were in primary forest habitats on stream terraces, hillsides, and ridgetops.

Fig. 10

Reproduction of Meyer's (1898) color plate of “Sciurus sarasinorum” ( =  Prosciurillus alstoni). The top portrait was rendered from the specimen collected at Mapane, the bottom from the squirrel obtained at Usu (see gazetteer and the account of P. alstoni).

TABLE 10

Summary of Habitat at Trapping Sites, Stomach Contents, and other Relevant Information for Specimens of Rubrisciurus rubriventer Collected by Musser in Central Sulawesi, 1973–1976 Collection locality, specimen number, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). Six of the collection localities (Sungai Oha Kecil, Sungai Miu, Sungai Sadaunta, Tomado, Kuala Navusu, and Sungai Tolewonu) are in tropical lowland evergreen rain forest; lower montane rain forest describes the places on Gunung Kanino. With two exceptions, all squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

From trapping records, the species is far more common than sightings would suggest—Rubrisciurus is quiet, wary, and easily startled. Although he spent every day in the forest checking traps and collecting botanical samples, Musser seldom saw Rubrisciurus; when he did, it was usually only as a reddish streak disappearing into the undergrowth or through the understory crowns. Once he saw two near camp at the Sungai Tokararu, one knocked over a live trap, the other scampered along a trunk on the ground, jumped off and poked around, then dashed into the undergrowth.

Two other sightings illustrate the squirrels' understory habits. On a hillside above the Sungai Tokararu, Musser had rebaited a rat trap and afterwards was sitting quietly on the dry leaf cover listening to sounds in the forest. He heard something upslope and after a few seconds a Rubrisciurus passed about 5 ft from him, progressing downhill in slow bounds alternating with an ambling walk. It held its tail out behind its back in a low arc. The squirrel did not react to Musser's presence, ambled by, looked around, then bounded down the slope over the litter and through the undergrowth until it was out of sight.

Musser enjoyed another rare encounter, this time in oak-chestnut forest on Gunung Kanino at 1500 m. He was sitting on a tree trunk and heard a squirrel move the dry leaf litter along the ridge, ambling and bounding along past him about 5 ft away. It bounced to a nearby chestnut, climbed over the roots and up one of the trunks to about 4 ft from the ground, straddled the trunk with its head down and its tail stretched out behind, looked downslope, uttered a few low growls, jumped to the ground, then bounded over the ridge and disappeared into the forest.

Rubrisciurus nests in tree cavities not far from the ground. Usma, one of Musser's helpers, described how he had once helped locate a nest. The villagers where he lived regularly used dogs to find the squirrels in the forest and then chase them to their nest. During one hunt, Usma located a nest in an old but still growing pohon torode (Pterospermum celebicum), with a trunk about 2.5 ft in diameter near the base. The base was hollow, forming an inverted cone-shaped cavity inside the trunk extending from the roots up for about 10 ft. The cavity was accessed by the squirrel through a hole about 4 ft from the ground. The original entrance to the cavity had been gnawed around the margins to form a larger opening. Wedged in the cavity between the opening and the roots was a large globular nest, about 1 ft in diameter with a single entrance, constructed entirely of the long, black sturdy fibers from a sugar palm (Arenga pinnata). The conformation of this nest, its construction material, and its placement, according to Usma and the few others we spoke to who were familiar with the squirrel's habits, were typical—large globular nests not far from the ground in cavities in the trunks of large trees.

In tropical lowland evergreen forest between the coast and about 1000 m, Pterospermum celebicum is common. Older trees contribute to the canopy; younger trees and saplings are familiar components of the understory, as well as in more open places in the forest. Musser never saw a tree with a basal diameter greater than 3 ft, and most of those that large had already died and fallen to the ground. It grows along stream terraces, hillsides, and ridgetops. The sugar palm is found in the same forests all the way up to the lower limits of lower montane forest. Probably any large canopy-forming species that develop spacious cavities within the basal portion of the trunk could be used as a nest site. Strangler fig emergents in which the host tree has nearly or completely decayed are also likely candidates for protected nesting sites.

The diet of Rubrisciurus rubriventer consists of fruits, seeds, and insects. Remains of a variety of fruits and seeds were found in stomachs (tables 10, 57). We could identify figs (stomachs would be distended with chopped figs, pulpy endosperm, and small seeds); tan mash, possibly from pangi fruit; seeds from the monocot vine, Rhaphidophora sp.; fruit (the pulp) from trees in the Sapotaceae; seeds from the understory tree pohon pangi (Pangium edule); fruit from pohon dongi (Dillenia serrata), another understory tree; seeds of the ginger, Etlingera celebica; seeds from the magnolia pohon uru (Elmerrillia ovalis); and fruit of Pandanus spp. Caches of acorns from Lithocarpus could be seen in places throughout the forest but we never found anything in the stomachs of Rubrisciurus resembling acorn mash, and Musser never saw the red squirrel eating acorns that had fallen to the ground or were still attached to branches. Still, Lithocarpus fruit cannot be discounted as part of the diet.

Four kinds of fruit are regularly consumed by Rubrisciurus. Many species of fig form components of the forest habitats within the altitudinal range of the squirrel. Several species are limited to the understory, especially along banks of streams where ripe figs fall from the trees and litter the ground. Fruiting tall canopy and emergent species of strangler and other figs attract birds, canopy tree squirrels (Prosciurillus), and macaques during the day and fruit bats (Pteropidae) at night. The fruits not eaten in the crown of the tree eventually drop to the ground where they are accessible to Rubrisciurus, nocturnal rats, and other terrestrial mammals.

Pangium edule is common in the understory of forests along river terraces and hillsides in tropical lowland evergreen rain forest from the coastal lowlands to about 1100 m. The fruit is large (about 6 in. long and 3–5 in. wide) and woody, containing large and very hard seeds. Near camp on the Sungai Oha Kecil, Musser watched a Rubrisciurus climb a pangi, jump to a branch bearing fruit, bite the stem so the fruit crashed to the ground, then ran down the tree to disappear into the undergrowth because the squirrel had seen Musser. Remains of these large opened seeds are scattered over the stream terraces; here and there are caches beneath tree roots and rocks. The sound of the loud gnawing on the tough seed by the red squirrel travels through the forest, and often provides the only indication of the squirrel's presence.

The ginger is scattered through the lowland forests where it is most commonly seen in openings where secondary growth begins to cover old treefalls. When mature, the leafy stalks may be 12 ft high and the fruit forms huge clumps close to the ground—easily accessible to Rubrisciurus. Rhaphidophora sp., the monocot vine, is common in lowland rain forest. The fruit (5 × 1 in.) is composed of small seeds and an outside hard polygonal portion attached to a filamentous white woody base. Along streamside forest near Tomado, Musser startled a Rubrisciurus feeding on fruit from this vine, and partially eaten fruits were found at many places along the transect line.

With few exceptions, a predictable suite of insects was found in stomachs of many red squirrels: numerous remains of soldier and worker termites (head capsules, often still attached to partially digested bodies, bodies and legs, and sometimes intact termites), all representing Rhinotermitidae (Isoptera); legless larvae of beetles, Coleoptera (usually without head capsules, apparently the squirrel removes the head and ingests only the thorax and abdomen of the larva), which are common but not as abundant as the termites; and pupae of carpenter ants, occasionally with an adult ant (Formicidae, Camponotus). Some stomachs were packed with this combination of insect remains, always with the termites being the most abundant; other stomachs were distended with remains of the insect suite mixed with fruits and seeds. Rhinotermitid termites, legless beetle larvae and those with tiny and short legs, and pupae of carpenter ants are part of a community found only in dead and rotting wood, especially pieces partially covered by leaf litter and soil (D. Grimaldi, personal commun., 2009). Musser often encountered deeply excavated sections of wet and rotting tree trunks and limbs lying on the forest floor as well as the erect bases of rotting tree and palm trunks. He dug into several undisturbed sections and found adult Coleoptera, legless beetle larvae, and sometimes termites. Rubrisciurus rubriventer travels and forages on the ground as well as in the understory canopy; on the ground, it clearly digs into rotting wood and exposes the insects.

The squirrel must also pick insects off leaf litter, tree trunks, and limbs in the understory canopy. One stomach contained a large adult beetle mixed with fruit mash. Another held buprestid beetle larvae, a macrolepidopteran caterpillar, and large margarodid scale insects mixed with the usual combination of termites and legless beetle larvae. Adult beetles are on the ground and in the trees; buprestid larvae are found beneath rotting bark, both on trunks and limbs decaying on the forest floor and on lower limbs and trunks of living trees; the scale insects occur on the surface of the bark, usually on the trunk or in tree crowns, some occur on wood on or near the ground.

The skull of Rubrisciurus is large and sturdy, with strong procumbent incisors, a long rostrum relative to size of the skull, only slight cranial flexion, prominent temporal ridges that combine to form a pronounced sagittal crest reflecting significant temporal musculature, a large and sturdy platform for the insertion of the superficial masseter, and a large, robust mandible (see fig. 6). That combination of traits among Sulawesi's endemic tree squirrels—Rubrisciurus and species of Prosciurillus (compare the skull of Rubrisciurus in fig. 6 with those of Prosciurillus depicted in figs. 12–Fig. 1314)—is restricted to Rubrisciurus. This morphology is well adapted to gnawing open large and tough woody nuts, such as those from pangi. It is also structurally suitable for excavating rotten tree limbs, trunks, and stumps. The wood is soft and pulpy and no special adaptations to claws would be necessary for the job. But in addition to front claws, the squirrel may depend on its large and strong incisors, especially the procumbent uppers (see fig. 6) to dig into the decaying wood. Also, the rostrum, relatively long compared with the relatively very short rostrum of the other species of Sulawesi tree squirrels, may contain a greater area of nasal epithelium providing the enhanced olfactory acuity necessary for detecting insects in decaying wood. Musser did not see a red squirrel actually digging into decaying parts of old treefalls, but did surprise one squirrel that had been sniffing about a small rotting tree trunk on the ground.

In contrast to Rubrisciurus rubriventer, the other Sulawesi tree squirrels—Prosciurillus alstoni, P. topapuensis, and P. murinus (and the other members of the P. leucomus and P. murinus groups)—have a very short rostrum compared to skull length, strong cranial flection, faint temporal ridging, and no sagittal crests; and also the anteroventral corner of the ventral zygomatic root is relatively thinner and the outer osseous surface only slightly roughened to accommodate the insertion of the superficial masseter (see figs. 12–Fig. 1314). The morphology suggests a diet of softer foods than those described for Rubrisciurus, and that locating certain dietary elements by olfaction may not be as important in these squirrels as in Rubrisciurus. All three species of Prosciurillus introduced above consume soft fruits (figs are an example) as well as insects (table 57). Contents of stomachs held no indication that tough nuts were taken, such as those from pangi and oaks. The insects in the stomachs examined are macrolepidopteran and geometrid caterpillars along with beetles, scale insects, and cockroaches (most of which are gleaned from surfaces of foliage and bark); and buprestid beetle larvae dug from beneath bark (see ecology accounts for the different species). Contents of stomachs also point to arboreal termites in Termitidae as part of their diet. Nests of these insects are fastened to limbs in tree crowns and easily scratched open by the squirrels, causing the termites to pour out of the nest onto the branch to quickly become easy prey. The suite of insects living in rotting wood—terrestrial termites in Rhinotermitidae, legless beetle larvae, and carpenter ant pupae—sought by Rubrisciurus was not found in the any of the stomachs we examined from Prosciurillus.

Rubrisciurus rubriventer's large body size (500–800 g) and long legs, its bright red coloration and bushy tail, its wary and quiet nature, its habits of foraging and traveling through tree crowns in the understory layer and along the ground, and nesting in the base of hollow trees in tropical rainforest habitats are a combination seen in two other species, both in a different phylogenetic lineage (Sciurinae) than that of Rubrisciurus (Nannosciurinae), and occurring on another continent. The northern Amazon red squirrel, Sciurus igniventris (500–900 g), and southern Amazon red squirrel, Sciurus spadiceus (600–650 g) are endemic to tropical rainforest habitats in the Amazon Basin of South America (Emmons and Feer, 1990: 167–168). Each is red, large-bodied, long-legged, and bushy-tailed (see pl. 19 in Emmons and Feer, 1990). Both are wary, quiet, and travel in the understory canopy or along the ground; neither one travels through the upper canopy of the forest. Palm nuts along with other kinds of large seeds and fruit form their diets, and both squirrels can be located in the forest by the sounds of their gnawing on the tough palm nuts. Insects, however, have not been recorded as part of their diets (although we are not aware of any study examining contents of stomachs). There is apparently an ecological niche in New and Old World tropical forests centering on understory habitats occupied by diurnal tree squirrels sharing a close similarity in morphology, diet, and other ecological parameters, but with different evolutionary histories rooted in widely separate lineages within Sciuridae.

Ectoparasites

In addition to the sucking louse Hoplopleura rubrisciuri, n. sp. (see description in a following section), the flea Medwayella rubrisciurae (Siphonaptera, Pygiopsyllidae) has been recorded from vouchers of Rubrisciurus rubriventer collected at Tomado and Sungai Sadaunta in the west-central region of Sulawesi's central core (Durden and Beaucournu, 2006). Another species of flea, Macrostylophora theresae (Ceratophyllidae), parasitizes three species of endemic Sulawesian murid rodents (Bunomys fratrorum, Paruromys dominator, and Rattus xanthurus). However, Durden and Beaucournu (2006: 224) speculated that Rubrisciurus rubriventer might be the true host because other members of this flea genus are ectoparasites of squirrels, especially larger-bodied tree squirrels, throughout Southeast Asia. Rubrisciurus rubriventer is also parasitized by immature stages (larvae and/or nymphs) of hard ticks (Acari, Ixodoidea, Ixodidae) belonging to four different genera: Amblyomma sp., Dermacentor sp., Haemaphysalis sp., and Ixodes sp. (Durden et al., 2008). Amblyomma sp. and Haemaphysalis sp. have also been collected from Hyosciurus heinrichi, and Dermacentor sp. and Haemaphysalis sp. from Hyosciurus ileile (table 56). Collectively, in addition to the squirrel hosts, the four tick genera have been collected from a suite of other mammal hosts living in Sulawesi: shrews (the endemic Crocidura sp. and Crocidura elongate, and the commensal Suncus murinus), pigs (Sus celebensis, an endemic, and S. scrofa, feral domestic), rusa (Rusa timorensis, nonnative), water buffalo (Bubalus bubalis, nonnative), humans, domestic dog (nonnative), nine species of endemic murid rodents (Bunomys chrysocomus and B. fratrorum; Margaretamys beccari; Echiothrix centrosa; Maxomys hellwaldii, M. musschenbroekii, and M. wattsi; Paruromys dominator; Taeromys sp.; Rattus hoffmanni, R. xanthurus, and R. marmosurus), and four nonnative rats (Mus musculus; Rattus tanezumi, R. argentiventer, and R. exulans; Durden et al., 2008). Ectoparasitic laelapid mites were recovered from R. rubriventer pelt AMNH 101316 which was collected at Wawo, Pegunungan Mekongga, in southeastern Sulawesi at an elevation of 50 m in 1932.

Sympatry

The range of R. rubriventer on mainland Sulawesi overlaps that of all species of Prosciurillus, except for P. abstrusus, as well as both species of Hyosciurus (table 6). Along his transect in the northern portion of central Sulawesi, Musser trapped R. rubriventer in the same traplines, and sometimes in the same traps, as P. topapuensis, P. alstoni, P. murinus, and H. ileile (table 10).

Synonyms

None.

Prosciurillus Ellerman, 1947

The generic name Prosciurillus was generated after Ellerman had measured the orbit of hundreds of European and Asiatic squirrel skulls and discovered that species of the Indomalayan pygmy squirrels in Nannosciurus, the Sulawesian ground squirrel Hyosciurus, and Sulawesian small-bodied tree squirrel murinus all had a short orbit compared to all other squirrel taxa examined, less than one-fourth of the occipitonasal length. He (Ellerman, 1947: 259) proposed “Prosciurillus as a new genus for Sciurus murinus” and compared it to the South American pygmy squirrel Sciurillus, with which it has no close phylogenetic alliance as would be documented decades into the future (Moore, 1959; Mercer and Roth, 2003). Eleven years later, Moore (1958) redefined Prosciurillus, describing several anatomical traits associated with the skull that he thought to be diagnostic in addition to the relatively short orbit, and expanded the contents of the genus to include the Sulawesian leucomus (and presumably all the taxa associated with it, although not explicitly stated by Moore; see table 11).

TABLE 11

Allocation of Scientific Names Associated with Species in the Prosciurillus leucomus Group as Presented in Primary Checklists of Mammals from 1940 to the Present The combination of generic and specific names as originally proposed is listed in their published chronological order. See the accounts of species for names of authors and dates of publication.

Moore's (1959: 176) expanded report of relationships among living squirrels, which contained the results of his survey of cranial characters in the Sciurinae, brought together Prosciurillus with the Sulawesian Rubrisciurus and Hyosciurus, as well as the Sundaic-Philippine Exilisciurus in the subtribe Hyosciurina of the tribe Callosciurini. Except for Exilisciurus, Moore's hypothesis of phylogenetic relationships for Prosciurillus has been unambiguously supported by analyses of the nuclear IRBP and mitochondrial 12S and 16S ribosomal DNA used by Mercer and Roth (2003) to recover a squirrel phylogeny that included a monophyletic group containing Rubrisciurus, Prosciurillus, and Hyosciurus separate from a cladistic cluster formed by Callosciurus, Sundasciurus, and their relatives. Within the Sulawesian clade, the species of tree squirrels in Prosciurillus are more closely related to Rubrisciurus than to the morphologically divergent ground squirrels in Hyosciurus. The phylogram of relationships generated by Mercer and Roth excludes the species of pygmy squirrels in Exilisciurus from the Sulawesian clade (see introductory discussion in the account of Rubrisciurus).

The short orbit (indicated by the lacrimal and posterior margin of the zygomatic plate situated even with the second upper molar) and lack of transbullar septa in more than 50% of large samples (see Moore, 1959: 163) are the strongest cranial traits distinguishing Prosciurillus from most genera of Nannosciurinae. But among the Sulawesi endemics, a short orbit is also common to Rubrisciurus and Hyosciurus, as is either the complete absence or low frequency of occurrence of transbullar septa. All three genera also possess third premolars and exhibit parallel upper tooth rows. Otherwise, Prosciurillus is easily distinguished from Rubrisciurus and Hyosciurus by the following combination of traits (see comparative measurements summarized in table 3, color plates of live poses in figs. 9 and 10, and compare skulls illustrated in figs. 6, 12–Fig. 1314, 36, and 37): (1) short face and much smaller in body size (table 2), the two smaller-bodied species often referred to as pygmy tree squirrels (but still much larger than the species in Nannosciurus and Exilisciurus, the true pygmy or dwarf tree squirrels); (2) upperpart dark brown or chestnut brown and without pattern, or lacking pattern except for black ear tufts, or possessing black ear tufts with nape patches behind ears, or exhibiting black ear tufts and prominent black middorsal stripe from neck to base of tail (no ear tufts, nape patches, or dorsal stripe in Hyosciurus; reddish orange fore-legs and feet, shoulders, thighs, and hind legs and feet in Rubrisciurus combined with black ear tufts); (3) underparts reddish orange to ochraceous, brownish gray, or dark gray washed with pale buff or silver (white or cream in Hyosciurus, reddish orange in Rubrisciurus; (4) hind foot short and broad, the typical configuration in tree squirrels, claws short and strongly recurved (hind foot long and slender in Hyosciurus, claws very long and only slightly curved); (5) tail slightly shorter than length of head and body (half the length of head and body in Hyosciurus; table 3); (6) three pairs of teats, one postaxillary and two inguinal (two inguinal pairs in Rubrisciurus; one abdominal pair and two inguinal pairs in Hyosciurus); (7) skull small and gracile with marked cranial flexion (robust, with strikingly reduced cranial flexion in Rubrisciurus and Hyosciurus); (8) rostrum short and wide, nasals and premaxillaries not forming a tube projecting beyond faces of upper incisors (rostrum moderately long in Rubrisciurus, very long in Hyosciurus where nasals and premaxillaries form a tube projecting anterior to faces of incisors); (9) nasals much shorter than length of frontals (53%–66% of length of frontals) and shorter than width of interorbital region (nasals as long as frontals or only slightly shorter, and nasals longer than width of the interorbital region in Rubrisciurus and Hyosciurus); (10) temporal ridges barely evident and reach occiput without coalescing to form a sagittal crest (stronger temporal ridges that combine to form sagittal crests in Rubrisciurus and Hyosciurus); (11) postorbital processes of the frontals about even with anterior wall of the braincase (well anterior to the braincase in Rubrisciurus); (12) anterior opening of the infraorbital canal lies slightly posterior to the premaxillary-maxillary suture and is concealed behind bony flange slightly or markedly projecting from ventral root of the zygoma, the anteroventral corner of the flange slightly thickened and marked on outer surface by a barely perceptible roughened elliptical area for insertion of the superficial masseter; (13) posterior border of bony palate located anterior to backs of the tooth rows, at about middle of each third upper molar (even with end of tooth rows or slightly caudad of tooth rows in Hyosciurus); (14) descending palatine vein transmitted through a notch (posterior maxillary notch; a foramen instead of a notch occurs in about 5% of all total skulls examined) at the posterolateral margin of bony palate just caudad and slightly medial to end of tooth row (vein is enclosed by bone forming a foramen in Hyosciurus); (15) pterygoid fossa narrow and deep, its lateral margin forming a high ridge—Moore's (1959) “ectopterygoid ridge”(lateral margin outlined by a low, inconspicuous ridge in Hyosciurus); (16) upper incisors proodont (procumbent), projecting forward (orthodont, oriented at right angle to rostrum in Hyosciurus); (17) upper third molar roughly triangular in occlusal view, about as long as it is wide (oblong in Rubrisciurus, much shorter than wide). Traits shared with Rubrisciurus and Hyosciurus are summarized in the diagnoses for those genera.

Fig. 11

Collection localities for samples of four species in the Prosciurillus leucomus group: P. leucomus, P. alstoni, P. weberi, and P. topapuensis. The collection site for Prosciurillus sp., which is represented by a subfossil fragment, is also indicated. Distribution of the fifth member, P. rosenbergii, in Kepulauan Sangihe is portrayed on the map in figure 28. Numbers key to localities described in the gazetteer where specimens are also identified by museum initials and catalog numbers. The inset map, right (rectangle in larger map, above), contains collection sites (1–12) for P. topapuensis scattered along Musser's transect from the Sungai Miu to Gunung Nokilalaki. The dashed contour line at 1300 m marks the approximate boundary between tropical lowland evergreen rain forest and tropical lower montane forest.

Fig. 12

Dorsal views of skulls representing species of Prosciurillus. Top row, left to right: P. alstoni (AMNH 226076; Kuala Navusu; ONL  =  46.6 mm) and P. topapuensis (AMNH 225504; Gunung Kanino; ONL  =  45.0 mm); we employ these two as exemplars of species in the P. leucomus group. Bottom row, left to right: P. abstrusus (AMNH 101378, holotype; Pegunungan Mekongga; ONL  =  38.2 mm) and P. murinus (AMNH 225496; Gunung Kanino; ONL  =  34.4 mm); these are the only species comprising the P. murinus group.

We provide accounts for the seven species of Prosciurillus, which are divided into two groups based on contrasts in coat color and patterning combined with physical body size. Squirrels of medium build (length of head and body  =  155–195 mm) exhibiting a combination of dorsal and ventral pelage coloration along with patterns associated with ear tufts, nape patches, and middorsal back striping comprise the P. leucomus group (P. leucomus, P. alstoni, P. weberi, P. topapuensis, and P. rosenbergii). Small-size squirrels (length of head and body  =  102–150 mm) with dark brown upperparts, slightly contrasting underparts, and generally without ear, nape or back displays (except for white fur on backs of the ears in P. abstrusus) form the P. murinus group (P. murinus and P. abstrusus).

The Prosciurillus leucomus Group

The first-named member of this assemblage, P. leucomus, was described by Müller and Schlegel in 1844. From then until now, 11 scientific names have been attached to the group, most of them described as species of Sciurus (table 11; also see Roux, 1910: 520). By 1940, Ellerman (1940: 375), in his compendium on the families and genera of living rodents, had transferred the taxa from Sciurus to Callosciurus and recognized a “leucomus Group” containing nine species. During the years to follow, the taxa associated with the leucomus cluster were shifted from Callosciurus to Prosciurillus (Moore, 1959; Corbet and Hill, 1992; Hoffmann et al., 1993; Thorington and Hoffmann, 2005) and the number of species recognized in primary checklists of mammals dropped to four (Laurie and Hill, 1954: 93), then two (Corbet and Hill, 1992: 304; Hoffmann et al., 1993: 436), and eventually was elevated to three (Nowak, 1999: 1270; Thorington and Hoffmann, 2005: 785). We recognize five species (table 11).

Our hypotheses of species-boundaries are based on results from our qualitative study of variation in coat-color patterns and quantitative analyses of morphometric variation in cranial and dental traits, bolstered by insights from geographic and altitudinal distributions determined from collection localities of voucher specimens. Different chromatic patterns and pelage traits (variation in coloration of upperparts and underparts, presence or absence of ear tufts and when present their coloration and degree of expression, and presence or absence of nape patches and middorsal stripes) and geographic distributions of the various chromatic combinations provide the primary diagnosis for each species (summarized in table 12). Morphometric distinctions parallel the chromatic contrasts but are less conspicuous compared with the striking variation in color patterns and appreciated only with measurements from large samples. All the species are similar in body size and cranial and dental dimensions (tables 15–TABLE 1617). They are intermediate in physical size (130–210 g) between the larger-bodied Indomalayan tree squirrels Callosciurus prevostii (250–500 g) and Sundasciurus hippurus (260–365 g) and the smaller-bodied tree squirrels Callosciurus adamsi (115–154 g) and Sundasciurus lowii (60–120 g), and more similar to the common Callosciurus notatus (150–315 g) and C. nigrovittatus (147–257 g); see Medway (1969) and Payne et al. (1985). Among the Sulawesi endemics, Prosciurillus leucomus and its four allies are each physically much smaller than Rubrisciurus rubriventer but larger than each member of the Prosciurillus murinus group (table 3).

TABLE 12

Some Characteristics Distinguishing Members of the Prosciurillus leucomus Group Listed are pelage traits, extremes (mm) in ranges of selected external and cranial measurements, and weight (g) summarized from tables 14–TABLE 1516; ranges of collection elevations and general geographic distributions are included.

Definitions for three of the five species are enhanced by their sucking lice parasites. Each of the three species of squirrels that are defined by color pattern of fur, morphometric traits, and explicit geographic boundaries support a unique species of Hoplopleura (see accounts of the sucking lice). Unfortunately, we did not recover lice were from pelts of the other two species (P. rosenbergii and P. weberi).

Gazetteer and Specimens Examined

Collection localities for the 177 examples of P. leucomus, the 107 specimens of P. alstoni, the eight specimens of P. weberi, the 78 specimens of P. topapuensis, the 39 examples of P. rosenbergii, and the single subfossil of Prosciurillus sp. studied are listed below. The number preceding each locality in the gazetteers for P. leucomus, P. alstoni, P. weberi, P. topapuensis, and P. sp. keys to a symbol on the map in figure 11. The distribution of P. rosenbergii on islands forming Kepulauan Sangir is featured on the map in figure 28.

Fig. 13

Ventral views of the skulls portrayed in figure 12. Prosciurillus alstoni and P. topapuensis are on top, P. abstrusus and P. murinus on the bottom.

Fig. 14

Side views of the skulls, along with mandibles, exhibited in figures 12 and 13. Top row, left to right: Prosciurillus alstoni and P. topapuensis. Bottom row, left to right: P. abstrusus and P. murinus.

Prosciurillus leucomus

1. Likupang, 01°41′N, 125°03′E, coastal plain near sea level: USNM 216786–92; SNSD B3431; ZMB 92614.

2. Teteamoet (several miles southeast of Likupang; see Raven's brief description of the place in Miller, 1917: 29), 01°40′N, 125°05′E (estimated from Raven's map), on coastal plain near sea level: USNM 216769–216785.

3. Pulau Lembeh, 01°26′N, 125°13′E (elevation of collection site is not recorded but highest point of the island is 447 m): Meyer (1896: 25) reported two specimens from this island. One (SNSD B3081) resides in the collection at Dresden, the other was sold (C. Stefen, in litt., 2008).

4. Manado (also spelled “Menado”), 01°30′N, 124°50′E, coastal plain near sea level: ANSP 14156; MZB 6235–37; RMNH 13343 (paralectotype of Sciurus leucomus; specimen “a” in Jentink's catalog, 1888: 24), specimens “c” and “q” in Jentink's (1888: 24–25) catalog, RMNH 24434, and an uncataloged specimen; ZMA 19.867–19.871; ZMB 4119.

5. Lotta, 01°25′N, 124°49′E, coastal plain near sea level: ZMB 92616. Meyer (1896: 25) reported a specimen from Lotta.

6. Ajermadidi (also spelled Airmadidi), 01°26′N, 124°58′E, 200–300 m (estimated from Sheet NA 51-12): USNM 217823.

7. Rurukan, 01°21′N, 124°52′E, 900 m: AMNH 196569, 196563–68, 196570–73; ANSP14157; BMNH 1899.12.9.80, 1899.12.9.81, 1899.12.9.82; FMNH 8329; ZMB 13829/13929, 84939, 84940.

7. Tonsealama (also known as “Tonsea”), 01°19′N, 124°55′E, 600–700 m (estimated from Sheet NA 51-12): BMNH 1940.670, 1940.671 (“Tonsea”); MZB 6229–33.

8. Kema, 01°22′N, 125°03′E, coastal plain near sea level: RMNH 13344 (lectotype of Sciurus leucomus; specimen “b” in Jentink's catalog, 1888: 24).

9. Tondano, 01°19′N, 124°54′E, 600–700 m (estimated from Sheet NA 51-12): MZB 6234.

10. Gunung Masarang, 01°19′N, 124°51′E, 3500 ft (1067 m): ANSP 14154, 14155; BMNH 1897.1.2.15, 1897.1.2.16; SNSD B3430.

11. Tomohon, 01°19′N, 124°49′E, 700–800 m (estimated from Sheet NA 51-12): BMNH 1899.10.1.5; NMB 4246/1105, 9544/1197.

12. Temboan (on Kuala Kalait, “is a new clearing of eight houses and lies from Mt. Sapoetan south, 55° west and about six miles from Loboe,” wrote Raven in his field journal, 1916: 3 (in mammal division library at USNM), 01°03′N, 124°33′E (estimated from Raven's map), 500 m (estimated from Sheet NA 51-12): USNM 217822, 217825, 217826.

13. Amurang, 01°11′N, 124°35′E, on coastal plain near sea level: MZB 1500, 1501; SNSD B261, B622.

14. Tulabolo (“Toelabello” in Jentink's [1888: 25] catalog), 00°31′N, 123°16′E, 760 ft (230 m; see Fooden [1969: 137] for details): RMNH: specimens “i” and “j” in Jentink's (1888: 25) catalog (paralectotypes of Sciurus leucomus occidentalis).

15. Gorontalo, 00°31′N, 123°03′E, coastal plain near sea level: SNSD B168 (holotype of Sciurus leucomus occidentalis). “Panybie”: RMNH: specimen “l” in Jentink's (1888: 25) catalog. “Modélido”: RMNH: specimen “m” in Jentink's (1888: 25) catalog. (Specimens “l” and “m” are paralectotypes of Sciurus leucomus occidentalis.) The last two localities are near Gorontalo (see Meyer, 1896: 26) but we don't know exactly where.

16. Limboto (also spelled Limbotto), northwest shore of Danau Limboto, 00°37′N/122°57′E, 0–100 m (estimated from Sheet NA51-14): RMNH: specimen “p” in Jentink's (1888: 25) catalog (paralectotype of Sciurus leucomus occidentalis).

17. Bumbulan, 00°29′N, 122°04′E, coastal plain near sea level: AMNH 152916–20, 152922–31, 152933–37; MZB 6239–42, 6246–48.

18. Paguat (also spelled Pagowat), 00°26′N, 121°54′E, coastal plain near sea level: RMNH specimen “k” in Jentink's (1888: 25) catalog (paralectotype of Sciurus leucomus and Sciurus leucomus occidentalis).

19. Sungai Paleleh (“I went inland about four or five miles over the mountains and made camp at the edge of the Paleleh River, which is a small brook … with steep mountains or hills on all sides” [Raven, in Miller, 1915: 23]), 00°59′N, 121°49′E (estimated from Raven's map), 700 m (estimated from Sheet NA 51-14): USNM 200270–73.

20. Matinan (“Matinang” is an older spelling), 01°05′N, 121°42′E (for village near coast; specimens came from south of village at 600 m in foothills of Pegunungan Paleleh): AMNH 196547–49.

21. Gunung Matinan (also spelled “Matinang”), part of the broader Pegunungan Paleleh in the northwestern part of the northern peninsula, 1000 m: NMB 1198 (skin)/9543 (skull), paralectotype of Sciurus leucomus occidentalis.

22. Gunung Ile-Ile, 00°58′N, 121°48′E (one of the high places in the more expansive Pegunungan Peleleh traversing the northwestern part of the northern peninsula): AMNH 196559–62 (500 m), 196550–58 (1700 m).

23. Tolitoli, 01°03′N, 120°49′E (estimated from Raven's map), on coastal plain near sea level: USNM 200274.

24. Labuan Sore (spelled “Laboea Sore” on specimen labels and “Laboean Sore” on Raven's map), on east coast just north of Marantate, about midway between Towera and Toboli, 00°37′S, 120°03′E (estimated from Raven's map; see Bynum et al., 1997, who discussed this collection locality), 200 m (estimated from Sheet SA 51–1): USNM 218074–77.

25. Bumbarujaba (spelled “Bumbaroedjaba” on specimen labels), on highway crossing the peninsula between Tawaeli and Toboli, 00°43′S, 120°04′E (estimated from Raven's map), 915 m (according to Riley, 1924: 2): USNM 218708, 218709.

Specimens from the northern peninsula we studied but did not map are listed here. RMNH specimens “d–h,” “n,” and “o” (“Célèbes”) are entered in Jentink's (1888: 24–25) catalog. (Jentink's skin “d” was collected by S.C.J.W. van Musschenbroek, who was “resident” [ =  district officer] in Manado during 1875–76; see Van Steenis-Kruseman [1950: 378]. This animal therefore must be from NE Celebes. Other material that was collected by van musschenbroek includes the rats Maxomys musschenbroekii and M. hellwaldii, and the civet Macrogalidia musschenbroekii, all obtained near Manado. C. Smeenk, personal commun., 2010.) Six further paralectotypes of Sciurus leucomus are in RMNH: 39392 and 39393 (skeletons “a” and “b” in Jentink's [1887: 191] osteological catalog), and RMNH 39395–98 (skulls “c–f” in Jentink's [1887: 191] osteological catalog, all collected by E.A. Forsten in 1841 from “Célèbes” [ =  NE Celebes]. Three uncataloged skins from “N. Celebes” and a skin from “Minahasa, Celebes” are also housed in RMNH. SNSD B2745 and ZMB 92379, 92380, and 92615 are from “Main, Minahasa.” “Minahasa, N. Celebes” is the only locality designation for NMB 9546/1104 and SNSD B2745. Seven specimens at BMNH (1849.3.2.7, 1886.6.26.1, 1943.239–1943.243) are from “Celebes.”

Prosciurillus alstoni

1. Malakosa, Kuala Navusu, 00°58′S, 120°27′E (estimated from Sheet SA 51-1): 100 ft (30 m), AMNH 226076–81; 125 ft (38 m), AMNH 226082; 130 ft (40 m), AMNH 226083–85; 150 ft (46 m), AMNH 226086; 175 ft (53 m), AMNH 226087; 400 ft (122 m), AMNH 226088–96; 450 ft (137 m), AMNH 226097–99; 500 ft (152 m), AMNH 226100; 750 ft (229 m), AMNH 226101.

2. Tolai, Sungai Tolewonu, 01°04′S, 120°27′E (estimated from Sheet SA 50-8): 400 ft (122 m), AMNH 226510–12; 500 ft (152 m), AMNH 226513, 226514; 540 ft (165 m), AMNH 226515; 650 ft (198 m), AMNH 226516, 226517; 800 ft (244 m), AMNH 226518; 950 ft (290 m), AMNH 226519; 1000 ft (305 m), AMNH 226520, 226521; 1050 ft (320 m), AMNH 226522; 1100 ft (335 m), AMNH 226523, 226525; 1200 ft (366 m), AMNH 226524.

3. Pinedapa, 01°25′S, 120°35′E (estimated from Raven's map), 100 ft (31 m): USNM 219511–21, 219523–40.

4. Mapane, 01°26′S, 120°40′E, near sea level: SNSD B3826 (lectotype of Sciurus sarasinorum).

5. Tonkean, near Sinorang, 01°24′S, 122°30′E, 0–100 m (see Fooden, 1969: 137: SNSD B3178 (lectotype of Sciurus tonkeanus), B3179–B3186 (paralectotypes of tonkeanus; see Feiler, 1999: 407).

6. Usu (“Oesoe” on old maps; also spelled “Ussu”), 02°36′S, 121°06′E, coastal plain at the northern end of Teluk Bone, 0–100 m: NMB 1199 (skin), 8080 (skull), paralectotype of Sciurus sarasinorum.

7. Wawo, on the plain between the coast and western foothills of Pegunungan Mekongga (also spelled “Mengkoka”), 03°41′S, 121°02′E, 50 m: AMNH 101329–39, 101347.

8. Pegunungan Mekongga, Masembo, which is southeast of Wawo and the highest place in the southern portion of Pegunungan Mekongga (see maps and discussion in Heinrich [1932] and Stresemann [1940]) 03°35′S, 121°15′E (for the Pegunungan), 550 m: AMNH 101340–46.

9. Mowewe, 04°10′S, 121°52′E, approximately 500 m: NMB 1626 (skin), 4243 (skull), lectotype of Sciurus mowewensis. Sungai Ahua: NMB 1627 (skin), 4244 (skull), paralectotype of Sciurus mowewensis.

10. Lalolei (spelled “Lalolis” on specimen tags and some maps), 03°57′S, 122°03′E, 300 m: AMNH 101325–28.

11. Pulau Buton, off the coast of the southeast peninsula, topographic relief ranges from sea level to 1190 m: MZB 6250, 6251. We do not know where on the island these two squirrels were collected and simply placed a dot randomly within the island's outline. Sody (1949: 107) examined the pair and noted that “These two animals have been a long time in the Museum [MZB], until lately stuffed, now made to study skins. On the glass of the case, in which they were exhibited, was an indication: ‘Sciurus tonkeanus Meyer. Boeton, Mohari leg.’ I am not able to say much more.”

12. Pulau Kabaena, off the coast of the southeast peninsula, topographic relief ranges from sea level to 1570 m: SMF 721 (holotype of Sciurus elbertae), 4878 (both specimens, skulls only, were kindly examined for us by G. Storch). Schwarz (1911: 639) identified the type locality as “Eempuhu, East Kabaëna.” We could not find Eempuhu on any maps or in any gazetteers consulted and simply placed a dot on the eastern side of the island.

Prosciurillus weberi

1. Masamba, 02°34′S, 120°19′E, coastal plain, 0–100 m: MZB 6252, 6253. 2. Palopo (“near Palopo”), 03°01′S, 120°13′E, 0–100 m: BMNH 94.7.4.6 (a skin only, which is one of the specimens upon which Jentink's [1890] original description of Sciurus weberi is based, and is a paralectotype); MZB 6254, 6256; RMNH 13342 (lectotype of Sciurus weberi); ZMA 11.327 and 11.328 (each is a paralectotype of Sciurus weberi).

Prosciurillus topapuensis

1. Valley of Sungai Miu, Sungai Miu (right side), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 350 m: AMNH 224042.

2. Valley of Sungai Miu, Sungai Sadaunta (also spelled “Sidaonta” or Sidaunta”; tributary on right side of Sungai Miu), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 675 m: AMNH 224041.

3. Sungai Sadaunta, 2500 ft (762 m): AMNH 224581; 2700 ft (824 m), AMNH 224582.

4. Sungai Sadaunta, 2850 ft (869 m): AMNH 224584, 224585.

5. Sungai Sadaunta: 2900 ft (884 m), AMNH 224599, 224611.

6. Sungai Sadaunta: 3000 ft (915 m), AMNH 224586–88; 3050 ft (930 m), AMNH 226835.

7. Valley of Danau Lindu, Tomado (a village on western shore of Danau Lindu), 01°19′S, 120°03′E (estimated from Sheet SA 5-8), 1000 m: AMNH 226932 (caught at 1140 m).

8. Gunung Kanino, 01°17′S, 120°08′E (estimated from Sheet SA 50-8), 4600 ft (1402 m): AMNH 225501, 225502; 4650 ft (1418 m), AMNH 225504.

9. Gunung Kanino, 4700 ft (1433 m): AMNH 225503.

10. Gunung Kanino, 4800 ft (1463 m): AMNH 223532–35; 4900 ft (1509 m), AMNH 225505.

11. Gunung Kanino, 5050 ft (1540 m): AMNH 225506, 225507.

12. Gunung Nokilalaki, 01°13′S, 120°08′E, 7520 ft (2293 m): AMNH 223531.

13. Gunung Lehio, 01°33′S, 119°53′E, at or above 6000 ft (1829 m): USNM 218714–18, 218720–23.

14. Rano Rano, 01°30′S, 120°28′E, 6000 ft (1829 m): USNM 219483, 219484, 219486, 219487, 219490–501, 219503.

15. Besoa, 01°44′S, 120°13′E (for “Besoa District,” HOUSND, 1944); see description in gazetteer for Rubrisciurus rubriventer collection localities: USNM 219485, 219488, 219489, 219502. Along the “Lindoe Trail”: USNM 218719.

16. Gunung Topapu, approximately 02°S, 120°15′E (estimated from a copy of the map used by P. and F. Sarasin, the collectors of the specimen), 1550 m: NMB 1628 (skin), 4245 (skull).

17. Pegunungan Latimojong, 03°30′S, 121°23′E, 2200 m: AMNH 196534–44; 2800 m, AMNH 196545, 196546.

The following specimens were studied but the place where they were caught is not mapped.

Central Core, Tamalanti, 3300 ft (1006 m): BMNH 1940.691e, 1940.691f, 40.691g (holotype of Callosciurus leucomus hirsutus), 1940.691h–1940.691j. Laurie and Hill (1954: 156) noted that Tamalanti is a “Plantation between Rantekaroa [02°50′S, 119°50′E] and Koelawi [01°27′S, 119°59′E],” which was also the only information Musser and Paula Jenkins found when they searched through fieldnotes and other documents at BMNH.

Prosciurillus sp.

1. Ulu Leang I (a cave about 40 km northeast of Ujung Pandang in the Maros region; see map and description in Glover, 1976), 0–100 m: AMNH 269955 (subfossil fragment of a right dentary; see table 33 and fig. 29).

Prosciurillus rosenbergii

We examined all the specimens in RMNH and ZMT, and most from SNSD. Feiler's (1990) informative report documenting historical material in SNSD collected from the Kepulauan Sangihe did not tie individual specimens by catalog number to different island provenances, but Clara Stefen kindly provided that information for the few SNSD specimens we did not examine.

Kepulauan Sangihe, Pulau Sangihe (also spelled “Sangir”), 03°33′N, 125°30′E; BMNH 1876.10.21.4; FMNH 31846; RMNH 13351–53 (specimens “a–c” in Jentink's [1888: 23] catalog; paralectotypes of Sciurus Rosenbergii), RMNH 13354 (specimen “d” in Jentink's [1888: 24] catalog; paralectotype of Sciurus rosenbergii) and RMNH specimens “m” and “n” in Jentink's (1888: 24) catalog; SNSD 2551–53, 2559; ZMB 5128, 84973, 92377. Pulau Sangihe, Tabukan: SNSD 499, 500. (Chris Smeenk provided this note: one should be careful here. Although the specimens obtained by von Rosenberg are labeled “Sanghir”, in his manuscript notes von Rosenberg uses that name for the entire archipelago, and it cannot now be ascertained whether his material came indeed, all or part of it, from the main island P. Sangihe. Jentink's specimen “d” collected by Hoedt seems more reliable in this respect, as Hoedt labeled all his other specimens “Siao”. The specimens obtained from the dealer G.A. Frank again, are labeled “Sangir” without further specification.)

Kepulauan Sangihe, Pulau Siau (also spelled “Siao”), 02°49′N, 125°23′E: RMNH 13355–61 (specimens “e–k” in Jentink's [1888: 24] catalog; paralectotypes of Sciurus Rosenbergii), RMNH 13362 specimen “l” in Jentink's [1888: 24] catalog; lectotype of Sciurus Rosenbergii); SNSD 323, 2554, 2555–58, 2560, 2561.

Kepulauan Sangihe, Pulau Tahulandang (also spelled “Tahoelandang,” “Tagulandang,” and “Tangulandang”), 02°21′N, 125°25′E: SNSD B2842 (lectotype of Sciurus tingahi), B2843 and B2844 (paralectotypes of Sciurus tingahi).

Kepulauan Sangihe, Pulau Ruang (also spelled “Roeang”), Gunung Api, 02°18′N, 125°22′E for Pulau Ruang: SNSD 2847, 2848, 2850, 2851 (paralectotypes of Sciurus tingahi).

Prosciurillus leucomus (Müller and Schlegel, 1844)

Sciurus leucomus Müller and Schlegel, 1844: 87.

Sciurus leucomus occidentalis Meyer, 1898: 2.

Lectotype and Type Locality

The lectotype of Prosciurillus leucomus is an adult male (RMNH 13344, specimen “b” in Jentink's, [1888: 24] catalog) obtained by E.A. Forsten in 1840 from “Célèbes, Kéma.” It consists of a skin mounted in a live pose and a slightly damaged skull (extracted from the mount after Jentink's tenure at Leiden). The nasals are missing, there is a large hole in the right frontal bone, one upper molar and one maxillary premolar are missing, and four upper molars and one premaxillary molar are present but have fallen out of their alveoli; the mandible is intact and all teeth are present. Dental and some cranial measurements are listed in table 13.

TABLE 13

Age, Sex, and External, Cranial, and Dental Measurements (mm) for Holotypes Associated with Prosciurillus topapuensis (includes hirsutus), Prosciurillus weberi, and Prosciurillus leucomus (includes occidentalis) The taxa were originally described as members of either Sciurus or Callosciurus.

TABLE 14

Age, Sex, and External, Cranial and Dental Measurements (mm) for Holotypes of Prosciurillus alstoni (includes sarasinorum, mowewensis, and elbertae) and Prosciurillus rosenbergii (includes tingahi) The taxa were originally described as members of Sciurus.

Specimen “b” was one of eight specimens cataloged as types ( =  syntypes) by Jentink (1887: 191, 1888: 24). Following Chris Smeenk's suggestion (in litt., 2008), we select specimen “b” as the lectotype, following the rules promulgated in Article 74.1 of the Code (ICZN, 1999: 82). The other seven become paralectotypes: (1) specimen “a” (Jentink, 1888: 24), RMNH 13343, an adult female, a skin mounted in live pose and extracted skull collected by E.A. Forsten on April 6, 1840, from “Célèbes, Ménado”; (2) skeleton “a” (Jentink, 1887: 191), RMNH 39392, an adult skull and postcranial skeleton, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes”; (3) skeleton “b” (Jentink, 1887: 191), RMNH 39393, a juvenile skull and postcranial skeleton, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes”; (4) skull “c” (Jentink, 1887: 191), RMNH 39395, an adult damaged cranium with missing dentaries, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes”; (5) skull “d” (Jentink, 1887: 191), RMNH 39396, an adult skull with incomplete right dentary, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes”; (6) skull “e” (Jentink, 1887: 191), an adult damaged skull, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes”; and (7) skull “f” (Jentink, 1887: 191), a damaged skull, sex unknown, collected by E.A. Forsten in 1841 from “Célèbes.” Chris Smeenk (in his unpublished catalog of types at Leiden) has also included specimen “k” (Jentink, 1888: 25), RMNH 39394, in the type series, an adult male, mounted in live pose, no skull present, collected from “Célèbes, Pagowat.” Although no further details are given, this can only be the “Sciurus” collected by E.A. Forsten from Pagowat ( =  Paguat) during November 5–12, 1841, as mentioned in his diary, a copy of which (in an unknown hand) is preserved in the archives of the Leiden Museum (Chris Smeenk, in litt., 2008).

The type locality is Kema, 01°22′N, 125°03′E, near sea level on the coastal plain of the northeastern peninsula (locality 8 in gazetteer and map in figure 11), Propinsi Sulawesi Utara, Indonesia.

Chris Smeenk provided us with pages dealing with the Sulawesi squirrels from his manuscript version of the “Type-specimens of recent mammals in the National Museum of Natural History, Leiden,” and it is pertinent here to reproduce his remarks regarding the lectotypes and paralectotypes of “Sciurus leucomus”:

Emended Diagnosis

Prosciurillus leucomus is the first named of the five species in the P. leucomus group, sharing with those other members moderate body size and tail equal to, or shorter than, length of the head and body. It contrasts with the other four species by the following combination of pelage traits: (1) dorsomedial surface of each ear covered with long black hairs that project beyond the ear rim to form a prominent tuft; (2) inside of ears densely covered with bright ochraceous fur; (3) white, whitish buff, or grayish white patches of variable intensity and size on the nape behind the ears; (4) no black middorsal stripe extending from neck to base of tail; (5) reddish orange, orange-red, or ochraceous underparts; and (6) a geographic distribution restricted to the northern peninsula of Sulawesi where it ranges from coastal lowlands to montane forests.

Geographic and Altitudinal Distributions

Apart from the sample collected on Pulau Lembeh off the coast of the northeastern peninsula, all voucher specimens identified as Prosciurillus leucomus come from the mainland of the northern peninsula of Sulawesi (see gazetteer and map in fig. 11). Collection localities are scattered over the peninsula from the coastal plain near sea level at the northeastern tip (Likupang and Teteamoet, localities 1 and 2 on the map in fig. 11) to Bumbarujaba (locality 25) near the southern margin of the peninsula. Most localities lie between the coastal plain and 1000 m in what still is or once was tropical lowland evergreen rainforest habitats. The site at 1700 m in montane forest on Gunung Ile-Ile locality is the exception and the highest elevation recorded for any sample of the species.

Bumbarujaba is the most southern collection site for P. leucomus and how much farther south it may occur is unknown at present. Approximately 70 km south of Bumbarujaba in the mountains around Danau Lindu where Musser worked are the northernmost records for P. topapuensis; and Kuala Navusu, northeast of Lindu on the eastern coastal lowlands of the central core, approximately 100 km south of Bumbarujaba, is the most northern collection site for P. alstoni (see gazetteers and map in fig. 11). What kind of squirrel occurs in the landscapes between those two places and the southern end of the northern peninsula is unknown.

In addition to Prosciurillus leucomus, several other Sulawesi endemic mammals are recorded from Pulau Lembeh. There is another squirrel, P. murinus (see that account); a murid rodent, Rattus hoffmanni (Musser and Holden, 1991); a macaque, Macaca nigra (Fooden, 1969); the Celebes wild boar, Sus celebensis (Groves, 1981); and the babirusa, Babyrousa babyrousa (Groves, 1980a; Grubb, 2005: 637, recognizes several species, listing the sample from Pulau Lembeh as B. celebensis). The closest points between island and mainland are less than a kilometer apart, and the Lembeh Strait is shallow, less than 50 m deep (Sheet NA 51-12). During periods of Pleistocene glaciation when sea level in the Indomalayan region dropped by at least 120 m (Bintanja et al., 2005) and possibly 200 m (Morley and Flenley, 1987), Lembeh would have been part of the mainland (see the map in Fooden, 1969: 65). With post-glaciation rise in sea level, rodent and other mammal populations on Lembeh were separated from the mainland. This scenario seems the most likely explanation for the occurrence of the three rodent species on the island, although we cannot rule out over-water dispersal. Whatever the process, squirrels in available samples of each species (as well as the other mammals referred to above) are similar in pelage coloration and morphometric traits to those in samples from the mainland, suggesting no significant genetic isolation between island and mainland populations.

Description

Müller and Schlegel (1844: 87) aptly described the diagnostic features of Prosciurillus leucomus (translated from the original Dutch by Chris Smeenk, in litt., 2008; the Dutch text is reproduced in appendix 2):

Samples from the northern peninsula of Sulawesi portray a squirrel of modest body size with a tail averaging as long as, or only slightly shorter than, length of head and body (length of head and body, 165–188 mm; length of hind foot, 43–47 mm; see table 15). The dense, uniformly thick (12–15 mm) coat covering upperparts of head and body is dark brown flecked with black and orange along the midline of the body from forehead to base of tail, but grading into brownish gray spotted with black and pale buff along sides of the body, forelegs, and hind legs. Dorsal surfaces of the front and hind feet resemble the head and back in most specimens; some are slightly darker or buffy gray. Coloration of the body fur results from the interplay of dark gray curly underfur; longer overfur composed of black hairs, each interrupted by a subterminal orange or pale buffy band; and black guard hairs barely projecting beyond the overhair layer.

TABLE 15

Descriptive Statistics for Measurements (mm) of Lengths of Head and Body, Tail, Hind Foot, and Ear, and for Weight (g), Derived from Samples of Prosciurillus leucomus, Prosciurillus alstoni, Prosciurillus weberi, and Prosciurillus rosenbergii^a Mean ± 1 SD, observed range (in parentheses), and size of sample are listed. Mean values were used to compute LT/LHB. Specimens measured are listed below.^b

TABLE 16

Descriptive Statistics for Measurements (mm) of Lengths of Head and Body, Tail, Hind Foot, and Ear, and for Weight (g), Derived from Samples of Prosciurillus topapuensis from the West-Central Core of Sulawesi^a Mean ± 1 SD, observed range (in parentheses), and size of sample are listed. Mean values were used to compute LT/LHB. Specimens measured are listed below.^b

This dorsal background is interrupted by distinctive color patterning on the head, ears, and neck. Top and sides of the muzzle are ochraceous, and the cheeks are either the same color as the top of the head or a grayish buff that extends to each nape patch. A prominent, dense black tuft covers the medial surface of each ear, projecting 5–10 mm beyond the free dorsal rim of the ear. Behind each ear on the nape is a large and conspicuous white, whitish buff, or whitish gray patch (20–30 mm long, 15–20 mm wide), its shape resembling an epaulet (pointed toward the posterior margin); and the inner surface of each pinnae is densely clothed with bright ochraceous hairs. The overall visual pattern evolves around an ear with an ochraceous center rimmed by black that is set off against a large whitish postauricular epaulet (see the color plate in fig. 9). While the black tufting is present in all geographic samples of P. leucomus, the nape patches vary in size, color, and frequency of occurrence; these aspects are addressed in the sections covering geographic variation and synonyms.

The short (5–7 mm thick) ventral coat ranges from bright reddish orange through orange-red to ochraceous; orange-red predominates in the samples. The hairs forming the ventral covering are pale gray along their basal half and deeply pigmented along the distal half.

The tail, equal to or slightly shorter than length of head and body (LT/LHB  =  95%–98%, see table 15), is covered in long hairs, each patterned by alternating black and buffy or orange bands. The overall effect is rings of black and buff with buffy bands outlining margins of the tail and long black hairs forming a black terminal tuft.

Females have six teats, positioned as one postaxillary pair and two inguinal pairs. Litter size has not been recorded for P. leucomus, but one young would be usual if this aspect of reproduction is like its allopatric relatives, P. topapuensis and P. alstoni (table 57).

The skull of P. leucomus closely resembles those of P. alstoni and P. topapuensis, which are illustrated in figures 12–Fig. 1314. Evident in those drawings is the convex dorsal curve of the skull reflecting pronounced cranial flexion, short and wide nasals and rostrum, wide interorbital region, postorbital processes that are even with the anterior curve of braincase, faint and widely spaced temporal ridges that do not coalesce into a sagittal crest, posterior margin of the bony palate situated slightly anterior to backs of the parallel tooth rows, wide pterygoid fossae (each triangular as seen from ventral view), conspicuous posterior maxillary notch in the bony palate between the end of the tooth row and anterior portion of the pterygoid fossa, proodont (procumbent) upper incisors, and small third molar compared with the larger second and third molars and fourth premolar. The dentary has a short coronoid process and deep ramus, and deeply concave (even angularly concave in some specimens) posterior margin between condyloid and angular processes. Cranial and dental measurements are summarized in tables 17 and 19.

Fig. 15

Specimen scores representing two population samples of Prosciurillus leucomus projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples are: filled circle  =  northeastern peninsula (Likupang, Teteamoet, Rurukan, Temboan; N  =  18); ×  =  western segment of northern peninsula (Bumbulan, Sungai Paleleh, Gunung Ile-Ile, Labuan Sore, Bumbarujaba; N  =  8). Ellipses outline 95% confidence limits for the specimen scores representing each population sample. See table 18 for correlations and percent variance.

Fig. 16

Reproduction of Anderson's (1879) color plate of “Sciurus alstoni” ( =  Prosciurillus alstoni).

Fig. 17

The region south of Malakosa in Sulawesi's central core, which shows Musser's two lowland camps (Kuala Navusu, Sungai Tolewonu) in lowland tropical evergreen rain forest (see the map in fig. 3 for geographic orientation within the geographically broader northern portion of the central core). Rubrisciurus rubriventer, Prosciurillus alstoni, and P. murinus were common in this region; Hyosciurus ileile also occurs here but was infrequently encountered. We designated Kuala Navusu as the type locality of Prosciurillus alstoni.

TABLE 17

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Combined Population Samples of Species in the Prosciurillus leucomus Group Mean ± 1 SD and observed range (in parentheses) are listed; size of sample follows the parentheses for P. rosenbergii.

Comparisons

The geographic distribution of P. leucomus is allopatric to the ranges of P. topapuensis and P. alstoni to the south in the central core of Sulawesi, and comparisons between P. leucomus and each of these two species will be presented in those accounts. No other samples of squirrels from regions on Sulawesi outside of the northern peninsula show the distinctive color patterns seen in P. leucomus (see the diagnostic traits compared in table 12).

Other than a close resemblance in body size, tail proportions, and some cranial dimensions, P. leucomus is also unlike P. rosenbergii, the only species occurring in the Sangihe Archipelago north of the northeastern tip of Sulawesi, and north of the distribution of P. leucomus. It is the the only member of the P. leucomus group with uniform dark chestnut upperparts and brownish gray or buff underparts. No ear tufts, nape patches, or middorsal black stripe mark the dorsal coat (table 12). Unfortunately, we do not have intact skulls from the samples of P. rosenbergii and cannot provide cranial and dental morphometric comparisons between it and P. leucomus.

Geographic Variation

Samples from throughout the geographic range of P. leucomus (the northern peninsula of Sulawesi) contain squirrels closely similar in body size (table 15). The noticeable geographic variation concerns coloration of the muzzle and the underparts, along with changes in color and extent of the nape patches. Most specimens from about the middle of the northern peninsula—in the region of Gorontalo (00°31′N, 123°03′E)—to the east have ochraceous muzzles and cheeks, prominent black ear tufts, large white or whitish buff nape patches, and reddish orange underparts. Squirrels in samples from west of Gorontalo show pale buff or gray muzzles and cheeks (as opposed to bright ochraceous), and exhibit considerable variation in extent and color of the nape patches. These patches may be prominent and white or whitish buff as in the squirrels inhabiting the peninsula east of the Gorontalo region; diluted, consisting of diffuse grayish patchs barely distinguishable from the rest of the neck (a few individuals from east of Gorontalo have diluted nape patches); or not present, the areas behind the ears being the same color as the rest of the neck and upperparts of the head and body. All these specimens retain a prominent black tuft projecting beyond the rim of each ear. Underparts of specimens in the western samples are paler: ochraceous is the dominant hue, a very few specimens exhibit reddish orange venters; reddish orange characterizes most specimens from east of Gorontalo, but some individuals show orange-red or ochraceous underparts. The variation in color of the nape patches and their extent has been the stimuli for recognizing the western peninsular samples as P. leucomus occidentalis (Meyer, 1898: 2). We elaborate on this variation and its significance in the section discussing synonyms.

The magnitudes of cranial and dental dimensions measured in our samples are similar (table 19). Mean values for certain dimensions average greater in the western samples than those from the northeastern end of the peninsula but the differences are not significant, as is reflected in figure 15 where specimen scores representing two population samples of P. leucomus—one from the northeast, the other from the western portion of the peninsula (identified in table 1)—are projected onto the first and second principal components extracted from principal-components analysis. The spread of scores along the first axis is primarily influenced by size, the larger (and sometimes older) adults spreading to the right, the smaller (and usually, but not always, younger) adults to the left. Covariation in most cranial variables spread the scores along the first axis with the most influential being breadths of the interorbit and rostrum, and lengths of the nasals, rostrum, diastema, and bony palate (table 18). The western squirrels have, on average, a larger facial skeleton, but the contrast is not significant as reflected in the complete overlap of the ellipses outlining the 95% confidence limits for the specimen scores representing each population sample.

Fig. 18

Specimen scores representing population samples of Prosciurillus leucomus from the northern peninsula (empty inverted triangle, N  =  26) and P. alstoni from the central core and southeastern peninsula (filled circle, N  =  63) projected onto the first and second principal components extracted from principal-components analysis. The ellipses outline 95% confidence limits for the specimen scores forming each cluster. Equations for the regression lines are: P. leucomus, Y  =  −0.331X+0.068 (F  =  11.30, P  =  <0.01); P. alstoni, Y  =  −0.133X−0.023 (F  =  3.42, P  =  0.059). Each regression line of the second principal component on the first component is clearly distinct from the other; while their Y-intercepts are significantly different (+0.068 versus −0.023; F  =  13.02, P  =  0.001), their slopes are not (−0.331 versus −0.133F  =  2.53, P  =  0.12). See table 20 for correlations and percent variance.

TABLE 18

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus leucomus from the Northern Peninsula Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 15.

The geographic variation in expression of nape patches within P. leucomus does not appear to have a counterpart in cranial and dental morphometric variation among our samples. However, other than the large series from Bumbulan, we have small numbers of squirrels from elsewhere in the western part of the peninsula, especially from that arc between Bumbulan and Labuan Sore at the base of the peninsula. Large samples are currently available from both west (Bumbulan, for example) and east (the Minahasa region) of Gorontalo, but we were still hampered in our investigation of cranial and dental morphometric variation because so many of the skulls are damaged, the result of sampling by shotgun. Clearly, the results we describe here will have to be tested by analyzing samples from regions now unrepresented by collections, and larger series of specimens containing intact skulls.

Morphology of available samples of sucking lice (Hoplopleura) varies slightly in accordance with host populations of P. leucomus but the samples of parasite and host are small. A few female and nymphal lice were found on a squirrel from Rurukan (leucomus morphology), east of the Gorontalo region, and on one collected at Labuan Sore (occidentalis morphology), to the west of Gorontalo at the base of the northern peninsula. Specimens in each sample of Hoplopleura differ slightly in shapes of the paratergal plates and lengths of their apical setae. However, males of these lice were not available for study (morphology of male genitalia is often the most important distinguishing character for different species of lice) and we consider the variation in the female paratergal plates to lie within the limits of a single species, Hoplopleura leucomus, n. sp. (see accounts describing the lice).

The variation in pelage traits among samples of squirrels collected over the northern peninsula roughly coincides with peninsular distributions of murid rodents and monkeys. Macaca hecki occurs from the base of the northern peninsula to the Gorontalo region, which coincides with the distribution of the color pattern variation in P. leucomus that has been recognized as occidentalis. Macaca nigrescens and M. nigra have allopatric ranges east of the Gorontalo area and extending to the northeastern tip and onto the offshore islands Pulau Lembeh and Pulah Talise (Fooden, 1969; Groves, 1980b, 2005); combined ranges of these two macaques are congruent with that of the typical form of Prosciurillus leucomus, which occurs east of the Gorontalo region all the way to the northeast tip of the peninsula and on Pulau Lembeh. The murids, Echiothrix leucurus, Bunomys fratrorum, Taeromys taerae, and Rattus xanthurus are also known only from this eastern segment of the peninsula (from Gorontalo eastward); their phylogenetic counterparts (Echiothrix centrosa; Bunomys andrewsi, B. penitus, and B. sp.; Taeromys hamatus; and Rattus marmosurus) range to the west of Gorontalo into Sulawesi's central core, or have been recorded only from the central core and the southeastern and southwestern peninsulae (Musser, ms; Musser and Carleton, 2005).

Ecology

We lack first-hand experience with P. leucomus in the wild and are unaware of any published observations. Judged from its close resemblance in body size and tail proportions to populations of squirrels from the central core of Sulawesi (P. topapuensis and P. alstoni) that Musser encountered, we suspect that P. leucomus is an habitué of the canopy, descending to the ground between gaps in the canopy and likely for some foraging. Soft fruits and insects probably comprise the diet.

Ectoparasites

The host-specific sucking louse Hoplopleura leucomus, n. sp. (described in a following section), is the only ectoparasite recorded from Prosciurillus leucomus (table 56).

Sympatry

The range of P. leucomus on mainland Sulawesi overlaps those of P. murinus, Rubrisciurus rubriventer, and the ground squirrel Hyosciurus ileile (table 6). Both P. leucomus and P. murinus have been collected on Pulau Lembeh off the northeastern coast of the northern peninsula (table 4).

Synonyms

Only one synonym is attached to Prosciurillus leucomus, which we discuss below.

Sciurus leucomus occidentalis Meyer, 1898: 2. LECTOTYPE: SNSD B168 (stuffed museum study skin and a skull; see table 13 for measurements), an adult female collected by Riedel in 1875. TYPE LOCALITY: Gorontalo, 00°31′N, 123°03′E, near sea level on the southern coastal plain of the northern peninsula, Propinsi Sulawesi Utara, Indonesia (locality 15 in gazetteer and map in figure 11).

To understand why we regard SNSD B168 to be the lectotype and Gorontalo to be the type locality, we must begin with Meyer's (1896) monograph covering the mammals of Sulawesi where he provided (pp. 25–26) an account of “Sciurus leucomus” and described the variation in expression of the white patch on the nape just behind each ear (see appendix 8 where the account is reproduced in the original German). Meyer set the context by noting Anderson's (1879: 252) observations derived from his visits to the museums in Paris and Leiden where he had examined specimens of “Sciurus leucomus.” According to Anderson,

Meyer studied 16 specimens from the Minahasa region (collected at Main, Manado, Lotta, and Amurang; see our gazetteer), two from Pulau Lembeh (locality 3 in our gazetteer), and two collected at Gorontalo (locality 15 in our gazetteer), on the northern peninsula far to the west of the Minahasa region. In his specimens at hand from the Minahasa district of the northeastern peninsula, the nape patches were expansive and white (white mixed with a few black-tipped or buffy-tipped hairs in some of our specimens), vividly contrasting with the large black ear tufts and brown dorsal fur, a pattern characteristic of leucomus from the northeast. The two specimens from Gorontalo, however, exhibited a different pattern. Both were adults as judged by characteristics of the skull and both had prominent black ear tufts, but one (B168) completely lacked the nape patches, and the other (857) exhibited only traces of the pattern: “Auf der anderen Seite zeigt von den 2 Exemplaren von Gorontalo das eine (B 168) keine Spur von Weiss, und es ist nach dem Schädel ein ganz altes Individuum, und das andere (857), ebenfalls adult, hat den Fleck nur sehr schwach entwickelt” (Meyer, 1896: 26).

Meyer also referred to material at Leiden that had been collected in the Gorontalo region. Specimens from Panibi, Modelido, and Limbotto (see our gazetteer) resembled the two Dresden specimens from Gorontalo in showing only faint nape patches or completely lacking them. On the other hand, Meyer admitted that examples from Tulabello, just east of Gorontalo, and Paguat, far to the west of Gorontalo, had prominent, whitish nape patches.

We see a similar range in variation in color and size of nape patches among our specimens stored in the USNM and AMNH. In USNM samples from the northwestern and western portions of the northern peninsula (Sungai Paleleh, Tolitoli, Labuan Sore, and Bumbarujaba; see the gazetteer), the black ear tufts are prominent but the nape patches are reduced in size and intensity as compared to those on squirrels from east of Gorontalo. The variation consists of individuals with modest white or whitish buff nape patches behind each ear (USNM 218074 from Labuan Sore, for example); specimens expressing diffuse patches, usually grayish or buffy white, barely distinguishable from the neck (USNM 218077, another squirrel from Labuan Sore); or a few specimens with no patches—at least the sides of the neck are indistinguishable from the bright brown fur tipped with buff over the head and body (USNM 200271 from Sungai Paleleh).

The variation in two geographic AMNH samples from west of Gorontalo is also illustrative. Twenty specimens come from Bumbulan (see gazetteer). One individual has large white nape patches that match the color and size of the patches characterizing the samples east of Gorontalo. Seven specimens have large, conspicuous nape patches, but they are dull compared with the bright patches seen in the eastern samples—gray or buffy gray instead of white. The patches are inconspicuous on most of the remaining specimens—small buffy areas behind the ears—and three lack the patches.

Sixteen AMNH specimens are from Matinan and Gunung Ile-Ile (see gazetteer), west of Bumbulan. All have prominent black ear tufts, similar in size to those on squirrels from east of Gorontalo. Six have smaller, inconspicuous buffy nape patches that slightly contrast with the rest of the fur covering the neck. Nape patches are conspicuous on squirrels in the remainder of the sample, but the patches are slightly smaller and duller (gray or buffy white) than those characterizing squirrels occurring east of Gorontalo.

In 1898, Meyer, under an account titled “Sciurus leucomus occidentalis n. subsp.” (p. 2), referred to his earlier report (Meyer, 1896) where he had described the whitish nape patches on the two squirrels from Gorontalo as being weakly developed or not present. In that report he had also speculated that the variation in expression of the nape patch seen on the two Gorontalo specimens might represent an intermediate pattern. At one extreme would be the pattern found in squirrels from the northeastern end of the northern peninsula: large, black ear tufts contrasting with expansive white nape patches. The sample of “Sciurus tonkeanus” (Meyer, 1896: 25) from the east-central arm of central Sulawesi, which lacks both black ear tufts and nape patches (ears and neck are the same color as the head and body; see our account of P. alstoni) would define the opposite extreme. Large black ear tufts combined with nape patches either reduced in size and intensity or absent would be the intermediate pattern, which is characteristic of squirrels inhabiting the northern peninsula in and west of the Gorontalo area.

Additional specimens collected by Paul and Fritz Sarasin and sent to Meyer for identification supported, in Meyer's view, his supposition. Meyer's identifications of the specimens collected by the Sarasins are recorded in his 1898 publication where he focused on contrasting variation in expression of the nape patches among the specimens. Five (three adult males, one adult female, and one juvenile female) from the Minahasa region (three from Tomohon, one from Kottabuna on the border of Minahasa, and one from “Minahasa”) exhibited the prominent white nape patches typical of leucomus (“spotted” [“gefleckte Form”] as Meyer described them). Two other squirrels, both males, were collected in the northern peninsula west of Gorontalo and lacked the nape patches (“unspotted” [“ungefleckte Form”]). One of these came from between Kottabongon and Bolang Mongondo at about 250 m, the other from the north side of the Matinan (“Matinang”) range at about 1000 m. After some discussion, Meyer (1898: 3) proclaimed that the “unspotted” form could be separated as a subspecies only from typical leucomus because of the apparent transition between the two forms: “Die ungefleckte Form lässt sich nur als Subspecies von leucomus abtrennen, da Uebergänge zwischen beiden vorhanden zu sein scheinen. …”

Some researchers who consulted only Meyer's 1898 report where he proposed the taxon occidentalis have assumed that Meyer regarded the two “unspotted” specimens collected by the Sarasins to be comparable to cotypes. But, as was the custom at that time, Meyer did not select a type, did not identify types of any kind, and did not designate a type locality. For him (Meyer, 1898: 3), the range of occidentalis extended from west of the Minahasa region (which is in the northeastern tip of the northern peninsula, the range of typical leucomus) to the Buol area (near Tolitoli; see gazetteer) in the northwest (“westlich von der Minahasa bis Buol”). His view was shaped not only by the two “unspotted” examples collected by the Sarasins and listed in the later 1898 publication, but also by the specimens he discussed in his earlier 1896 report: the two Dresden specimens from Gorontalo and the Leiden material collected around the Gorontalo region and farther west.

Without consulting both of Meyer's reports, any attempt to identify a type specimen and pinpoint the type locality is frustrating and has yielded different results from researchers. Ellerman (1940: 375), for example, listed occidentalis as being simply from “West Celebes.” In 1954, Laurie and Hill (p. 93) listed the type locality as “Between Kottabangon and Bolang Mongondo, north-western Celebes,” which suggests that the first of the two of the Sarasin's “unspotted” specimens listed by Meyer in 1898 would be the type. This locality designation was followed by Corbet and Hill (1992: 304). Feiler (1999: 407) in his catalog of types housed at Dresden, however, identified the “holotype” of occidentalis as SNSD B168, the squirrel mentioned by Meyer (1896) as being from Gorontalo. But Feiler, confusingly, listed the type locality as “Sulawesi, Nordseite der Matinang-Kette, etwa 1000 m hoch,” which is the collection locality of the Sarasin's second “unspotted” squirrel listed in Meyer's 1898 publication; Feiler does not record the presence of that specimen in Dresden.

Our attempt to examine all the specimens studied by Meyer has also proved frustrating. Some of the Dresden material Meyer discussed in his 1896 report is no longer in that institution (C. Stefen, in litt., 2008), but the Leiden specimens are still present in the Nationaal Natuurhistorisch Museum (C. Smeenk, in litt., 2008). Three of the five “white-spotted” squirrels collected by the Sarasins from the Minahasa region and identified in Meyer's 1898 publication are in the collection of the Naturhistorisches Museum Basel (L. Costeur, in litt., 2008; see gazetteer), another is in the British Museum (P. Jenkins, in litt., 2008). We also located only one of the Sarasin's two “unspotted” specimens, the example from the Matinan range (“nordseite der Matinang-Kette, etwa 1000 m hoch”), a skin and skull, which is also in the collection at Basel (see gazetteer). We have no idea where the other specimen is, the one collected between Kottabangon and Bolang Mongondo; it is not in Basel, Dresden, Leiden, or London.

SNSD B168, one of the two specimens from Gorontalo that Meyer (1896: 26) referred to by numbers and the one that Feiler (1999) regarded as the holotype, remains at Dresden (the other, 857, is no longer listed in the collection inventory; C. Stefen, in litt., 2008). It is currently identified in the inventory of mammal specimens at that institution, and on the skin and skull tags, as the “type” of occidentalis and the collection locality as “Gorontalo.” Clara Stefen kindly sent us color images of the skin and skull. The slightly stuffed nearly flat skin is intact except for a long tear in the throat, and most of the tail is missing. In ventral view, three pairs of large teats are clearly evident. On the dorsal surface the black ear tufts are prominent but there is no discernable trace of nape patches behind the ears. The occiput and part of the basioccipital region of the skull are missing, the mandible is intact and all upper and lower teeth are present.

SNSD B168 was identified by Feiler (1999: 407) as the holotype of occidentalis, and the Matinan range as the type locality. The specimen (NMB 1198/9543) from the Matinan range, however, is at Basel where it was cataloged in 1942 and is a male; it cannot define the type locality if the Dresden squirrel is indeed the type. However, SNSD B168, a female, is to be regarded as the lectotype (see below). Since Meyer (1896: 26) had explicitly stated that it came from Gorontalo, the type locality changes accordingly. Sometime between the publication of Feiler's 1999 catalog of types and the present, the skin and skull of SNSD B168, the supposed holotype of occidentalis in Feiler's catalog, was correctly linked to its provenance, Gorontalo, in the museum inventory.

The identification as “holotype” assigned to SNSD B168 by Feiler (1999: 407) should have been “lectotype” if we interpret correctly Article 74.5 (“Lectotype designations before 2000,” ICZN, 1999: 82): “In a lectotype designation made before 2000, either the term “lectotype,” or an exact translation or equivalent expression (e.g. “the type” [in this case, Feiler's use of the term “holotype”]), must have been used. …”

In light of the above, the other specimens discussed by Meyer (1896: 26, 1898: 2) now become paralectotypes. These include the squirrel at Basel (NMB 1198/9543) collected on the north slopes of the Matinan range, and the following six specimens from Leiden: (1) specimen “i” (Jentink, 1888: 25), RMNH 39399, a mounted skin still containing the skull, male, from Tulabolo, near Gorontalo, northern Sulawesi, collected on May 10, 1864 by C.B.H. Rosenberg; (2) specimen “j” (Jentink, 1888: 25), RMNH 39400, a mounted skin with skull still inside, female, from Tulabolo, near Gorontalo, northern Sulawesi, collected on May 10, 1864, by C.B.H. Rosenberg; (3) specimen “k” (Jentink, 1888: 25), RMNH 39394, a mounted skin without skull, male, from Paguat, northern Sulawesi, collected between November 5–12 by E.A. Forsten (also a paralectotype of P. leucomus; see that account); (4) specimens “l” (the skin, in Jentink, 1888: 25) and “h” (the skull, in Jentink, 1887: 191), RMNH 39401, a mounted skin and cranium, male, from Panibi, near Gorontalo, northern Sulawesi, collected between September 7–15, 1863, by C.B.H. von Rosenberg; (5) specimen “m” (Jentink, 1888: 25), RMNH 39402, a mounted skin still containing the skull, female, from Medelido, near Gorontalo, northern Sulawesi, collected between May 9–20, 1863 by C.B.H. von Rosenberg; (6) specimen “p” (Jentink, 1888: 25), RMNH 39403, mounted skin still containing the skull, sex unknown, from Limboto, northern Sulawesi, collected during January, 1876, by S.C.J.W. van Musschenbroek.

Prosciurillus alstoni (Anderson, 1879)

Sciurus alstoni Anderson, 1879: 252, pl. xxi (1878 is imprinted on the title page of the book, but the Corrigenda on the following page proclaims “The sanguine expectation that this work would have been issued during the past year has led to 1878 appearing on the title-page instead of 1879, the delay having arisen from circumstances over which the author had no control.”).

Sciurus tonkeanus Meyer, 1896: 25, pl. X, fig. 4.

Sciurus sarasinorum Meyer, 1898: 1 (1899: 21, pl.V).

Sciurus mowewensis Roux, 1910: 519.

Sciurus elbertae Schwarz, 1911: 639.

Holotype and Type Locality

The holotype of Sciurus alstoni (ZSI 9546) consists of a museum study skin and damaged skull and is an unsexed adult that was “purchased” (see Sclater, 1891: 21; Khajuria et al., 1977: 31). Some measurements are listed in table 14.

The type locality is the Malakosa region (northern portion of the central core of Sulawesi), Kuala Navusu, approximately 00°58′S, 120°27′E, in the coastal lowlands at 30 m, between Tanjung Pandendelisa (jutting into Teluk Tomini) and the mouth of Sungai Sausu to the southeast (locality 1 in gazetteer and identified on the maps in figures 11 and 17), Indonesia, Propinsi Sulawesi Tengah.

Our identification of the holotype of alstoni as a member of the P. leucomus group and selection of a type locality requires explanation, beginning with Anderson's (1879: 252) description of Sciurus alstoni, which is short but diagnostic (see also fig. 16):

Fig. 19

Specimen scores representing population samples of Prosciurillus alstoni and P. weberi (8-pointed star; N  =  5) projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples of P. alstoni are: filled circle  =  Pinedapa, N  =  19; filled triangle  =  Kuala Navusu and Sungai Tolewonu, N  =  32; cross  =  southeastern peninsula, N  =  11; star  =  Usu, lectotype of sarasinorum. Heavy arrow identifies score for the holotype of weberi; delicate arrows point to lectotype (top) and paralectotype (bottom) of mowewensis. See table 21 for correlations and percent variance.

Anderson provided measurements for “Length, muzzle to tail [our Length of Head and Body],” as 7.15 in. ( =  181.6 mm); “Length of tail without hair [our Length of Tail],” 6.50 in. ( =  165.1 mm); and “Length of tail with hair,” 8.30 in. ( =  210 mm). We have no comparable standard measurement for length of tail including the terminal tuft, so we measured the tail tufts of seven skins from Sungai Tolewonu and 19 skins from Kuala Navusu and added those values to lengths of tails ( =  tail vertebrae) for those specimens, obtaining the range 209–235 mm for the Tolewonu series, and 198–236 mm for the Navusu sample. As to the provenance of the specimen, Anderson wrote: “The locality from whence this species was obtained has not been accurately ascertained, but it is probably Borneo.”

Anderson's alstoni, with a few exceptions, disappeared from published checklists of squirrel species (Agrawal and Chakraborty, 1979, for example; Thorington and Hoffmann, 2005, who did list an alstoni, proposed by J.J. Allen in 1889, but that alstoni is a synonym of Sciurus nayaritensis, a fox squirrel occurring in northern Mexico and the southwestern United States; see p. 762 in that publication), checklists of rodents focusing on those native to the Indomalayan region (Chasen, 1940, for example), and publications devoted to mammals of a particular geographic region in the Indomalayan area, especially Borneo and the Malay Peninsula (Moore and Tate, 1965; Medway, 1969, 1977; Payne et al., 1985; Corbet and Hill, 1992). An early exception is Jentink's (1883: 118) “List of the specimens of squirrels in the Leyden Museum” where he recorded that Sciurus alstoni was “Characterized by the beautiful pure white tufting to the ears, which projects a considerable way backwards.” Jentink cited Anderson's description and noted that “no specimens were in the Leyden Museum.” Another is an entry for Sciurus alstoni in Sclater's (1891: 21) catalog of mammals in the Indian Museum where he noted that “The type and only specimen known is said to have come from Borneo,” indicating that a skin was present in the collection and that the specimen had been “purchased.” In Ellerman's (1940: 376) compendium on the families and genera of living rodents, he listed alstoni as a species of Callosciurus in a category “incertae sedis; not allocated to groups.” Another exception is Khajuria et al. (1977: 31) who provided “An annotated catalogue of the type specimens of mammals in the collections of the Zoological Survey of India [formerly the Indian Museum],” and entered information on the holotype of Sciurus alstoni. While Anderson (1879), Sclater (1891), and Ellerman (1940) noted the type locality to probably be “Borneo,” Khajuria et al. (1977: 31) narrowed it to “Indonesia, Kalimantan” but gave no reasons for doing so.

The most recent and only insightful allocation of Anderson's alstoni was made by Corbet and Hill (1992: 304) in their systematic review of the mammals of the Indomalayan region. They listed the combination “? Sciurus alstoni” among the scientific names associated with Prosciurillus leucomus, the provenance as “locality unknown,” and repeated Anderson's “probably Borneo.”

We have not personally studied the holotype of Anderson's Sciurus alstoni. We contacted Dr. Sujit Chakraborty at the headquarters of the Zoological Survey of India who informed us that the holotype is present in the collection and kindly provided us with values for some cranial measurements. The measurements, along with Anderson's description, measurements of body and tail, and the superb color plate depicting the squirrel in live pose (reproduced in fig. 16) do not describe any species of squirrel, no matter the genus, that is native to Borneo, as anyone can determine by simply thumbing through the color plates of squirrels (pls. 23–30) and relevant pages of descriptive text (233–243) in Payne et al.'s (1985) field guide to the mammals of Borneo. We know of no other species of tropical Indomalayan squirrel occurring outside of Borneo and west of Sulawesi, or in the Philippines that bears close resemblance to “Sciurus alstoni” (see the color plates depicting species of Indomalayan squirrels from the Malay Peninsula [Medway, 1969], Thailand [Askins, 1988], and “Southeast Asia” [Francis, 2008]; the statement is also based on Musser's study of Indomalayan squirrels stored in North American, Asian, and European museums).

The animal described by Anderson and depicted in his color plate is a member of the Prosciurillus leucomus group and an unambiguous representative of the same species from which the samples collected by Fritz and Paul Sarasin and described as sarasinorum (Meyer, 1898) and mowewensis (Roux, 1910) were obtained (see section discussing synonyms). Specimens from Kuala Navusu and Sungai Tolewonu collected by Musser (in AMNH), the sample from Pinedapa obtained by H.C. Raven (in USNM), and the squirrels collected from the southeastern peninsula by G. Heinrich (in AMNH) represent the same species. Values for length of head and body (181.6 mm) and length of tail (165.1 mm) for the holotype of alstoni fall within the range of variation listed in table 15 for these variables in the sample from Kuala Navusu and Sungai Tolewonu; length of tail relative to head and body length (91%) is also comparable, as is length of tail including the tuft (see above). The highlights of Anderson's description—dusky chestnut underparts, prominent white ear tufts, subapical blackish bands of the tail hairs that are tipped with white, blackish tail tip and the rest of the tail tinged with black and orange—match Musser's material laid out in front of us from Kuala Navusu and Sungai Tolewonu as well as the two examples of sarasinorum shown in Meyer's (1899) color plate (see fig. 10). Anderson's color plate of alstoni (see fig. 16), except for the underparts that appear faded, rendered orange rather than “dusky chestnut,” exhibits the same diagnostic pelage highlights described by him.

Where the holotype of alstoni was collected in Sulawesi is unknown. The specimen was purchased, according to Sclater (1891: 21) and Khajuria et al. (1977: 31), probably during Anderson's tenure as Superintendent of the Indian Museum, Calcutta (now the Zoological Survey of India, Kolkata), certainly before 1879. It had to have been collected within the range of the Prosciurillus exhibiting the alstoni pelage color pattern. Our voucher specimens characterized by that coloration and patterning come from lowlands and middle altitudes (31–1200 m) in the eastern portion of the central core of Sulawesi and throughout the mainland of the southeastern peninsula (see gazetteer and fig. 11). Forests of lowlands and mountains in the western portion of the central core are occupied by P. topapuensis, the distinctive P. weberi is found in lowlands at the southern sector of the central core west of the range of alstoni, and forests on the northern peninsula are inhabited by P. leucomus (see gazetteers and fig. 11).

There are two early travel routes in this range where the holotype of alstoni could have been collected. One extended from the Luwu region at the north end of Teluk Bone north to Mapane at the southern end of Teluk Tomini. Paul and Fritz Sarasin traveled this route in the late 1800s where they obtained a squirrel at Usu on the southern end and a specimen from Mapane at the northern end. The two specimens became the basis for Meyer's (1898) description of Sciurus sarasinorum. The other route transects the southeastern peninsula from Kolaka at Teluk Mekongga in the west to Kendari at the margin of Teluk Kendari in the east. The Sarasins traveled here in the early 1900s where they obtained the two specimens later described by Roux (1910) as Sciurus mowewensis. Earlier European travelers may have taken the same routes and possibly acquired Anderson's specimen along the way but we just do not know. The animal could even have been brought to Borneo by traders.

In the absence of any information about a collection locality for the holotype of alstoni, we turned to the International Code of Zoological Nomenclature (4th ed., 1999) for insight into selecting a type locality. One of the recommendations listed in that document (76A.1.4.) is pertinent here: “In ascertaining or clarifying a type locality, an author should take into account “as a last resort, and without prejudice to other clarification, localities within the known range of the taxon or from which specimens referred to the taxon had been taken.”

Within what is the known range of Prosciurillus alstoni defined by voucher specimens, we select Kuala Navusu (approximately 00°58′S, 120°27′E) as the type locality for the taxon. This is one of Musser's camps where during August–November 1975, he obtained 26 specimens of P. alstoni in lowland tropical evergreen rain forest between 30 and 229 m (see gazetteer). The campsite and surrounding region where Musser surveyed was located between the village of Malakosa (behind Tanjung Pandendelisa jutting into Teluk Tomini) and the mouth of Sungai Sausu (fig. 17). Prosciurillus alstoni was common in the forest there and also south of Kuala Navusu at Musser's camp on the Sungai Tolewonu (approximately 01°04′S, 120°27′E; fig. 17), one of the tributaries of Sungai Sausu, where during January and February 1976 he collected 16 specimens between 122 and 366 m (see gazetteer). The specimens from both places match Anderson's (1879) description of “Sciurus alstoni” in all aspects of body dimensions and pelage coloration.

Fig. 20

Specimen scores representing population samples of Prosciurillus alstoni from the eastern segment of central Sulawesi and the southeastern peninsula (filled triangle, N  =  63) and P. topapuensis from the mountainous western half of the central core of the island (empty triangle, N  =  50) projected onto the first and second principal components extracted from principal-components analysis. The ellipses outline 95% confidence limits for the specimen scores forming each cluster. Equations for the regression lines are: P. leucomus, Y  =  0.332X−0.056 (F  =  26.56, P  =  <0.01); P. alstoni, Y  =  0.176X+0.064 (F  =  7.99, P  =  <0.01). Each regression line of the second principal component on the first component is clearly distinct from the other; while their Y-intercepts are significantly different (−0.056 versus +0.064; F  =  31.49, P  =  <0.001). their slopes are not (0.332 versus 0.176; F  =  2.97, P  =  0.087). See table 22 for correlations and percent variance.

Emended Diagnosis

Prosciurillus alstoni shares with other members of the P. leucomus group moderate body size and a tail equal to or shorter than length of the head and body (tables 2, 14, 15). It contrasts with the other four species in the group by the following combination of pelage traits (see table 12): (1) dorsomedial surface of each ear covered with long white hairs projecting beyond ear rim to form a prominent tuft on most specimens, ears without tuft and concolorous with head and neck in a few individuals; (2) no bright ochraceous hairs lining inside of the pinnae, which is same color as fur on neck and head; (3) no nape patches behind the ears; (4) no middorsal black stripe extending along back from neck to base of tail; (5) dark reddish brown (approaching chestnut) underparts; and (6) a geographic range restricted to tropical lowland evergreen rainforest habitats on the eastern portion of Sulawesi's central core, the east-central peninsula, the southeastern peninsula, and islands offshore of that arm.

Geographic and Altitudinal Distributions

Collection localities of P. alstoni are from the eastern portion of Sulawesi's central core, the southern coastal plain on the east-central peninsula, the southeastern peninsula, and the islands of Buton and Kabaena (see gazetteer and map in figure 11). Collection sites range in elevation from 30 m (Kuala Navusu and Pinedapa) to 1200 m (Sungai Tolewonu), all in lowland tropical evergreen rainforest habitats (fig. 17). The distribution of collection sites indicates that P. alstoni is not sympatric with any other member of the P. leucomus group. The most northern record of P. alstoni is Kuala Navusu (00°58′S, 120°27′E). Approximately 100 km north of there is Bumbarujabu (00°43′S, 120°04′E) at the base of the northern peninsula and the southernmost collection locality for P. leucomus (see gazetteer and fig. 11). Between those two places along the eastern coast, assuming the presence of intact forest, the ranges of P. leucomus and P. alstoni either overlap (likely narrowly) or are parapatric. The pattern of contact is unknown because no members of the P. leucomus group have been collected along that coastal strip.

The mountains south of Bumbarujabu and west of Danau Poso in the western half of Sulawesi's central core—west of the range of P. alstoni—are inhabited by P. topapuensis, another member of the P. leucomus group. The boundaries of each range in that vast region of central Sulawesi between Teluk Tomini in the north and Teluk Bone in the south are unknown because no voucher specimens are available from there (see map in fig. 11). Members of the P. leucomus group have been collected only in the coastal lowlands bordering Teluk Tomini and lowlands around Teluk Bone. In the northern lowlands, samples of P. alstoni are from Mapane (01°26′S, 120°40′E) on the coast and inland a bit at Pinedapa (01°25′S, 120°35′E), 31 m. Westward toward the mountains, approximately 20 km from Pinedapa, is Rano Rano (01°30′S, 120°28′E), 1829 m, the easternmost collection site for P. topapuensis (see gazetteer and fig. 11). In this region, and possibly farther south along flanks of the mountains, P. topapuensis may occur only in montane forest formations (although it descends much lower, down to 350 m, in the western part of its range) and P. alstoni in lowland evergreen rain forests; only results from future surveys will provide a description of the boundary between these two species.

Southern lowlands fringing Teluk Bone have yielded two species in the P. leucomus group. Prosciurillus alstoni has been collected at the base of the southeastern peninsula at Usu (02°36′S, 121°06′E), and Masamba (02°34′S, 120°19′E), about 80 km west of Usu, is the easternmost collection site for P. weberi. Whether the two species overlap or their ranges abut in this lowland interval is unknown.

Prosciurillus alstoni may be restricted to habitats in tropical lowland evergreen rain forests. While P. leucomus, its northern neighbor, ranges from coastal lowlands to habitats in montane forest (coast to 1700 m), and P. topapuensis, its western relative, extends from tropical lowland forests at 350 m to upper montane formations at 2800 m, P. alstoni has yet to be collected above 1200 m (table 4). Montane areas within its range, however, have received little or no survey focusing on collections of small mammals with the exception of Pegunungan Mekongga in the southern portion of the southeastern peninsula. Samples of P. alstoni come from Wawo (03°41′S, 121°02′E) 50 m, on the coast west of that mountain range and Masembo (03°35′S, 121°15′E) on the lower flanks of the range at 550 m, all collected by G. Heinrich in the early 1930s. At higher elevations in lower and upper montane rainforest formations, Heinrich encountered only Rubrisciurus rubriventer (1400 m) and Prosciurillus abstrusus (1500 and 2000 m). He was an able naturalist and skilled hunter, daily walking the forests shooting birds and squirrels for various museums, and likely would have collected examples of P. alstoni if it occurred at elevations higher than 550 m.

Much remains to be learned about the actual geographic range of P. alstoni. Its distribution on the east-central peninsula, for example, is a mystery; specimens are from only a single locality on the southern coast, but the species probably occurs throughout the lowlands fringing the mountainous backbone of the peninsula. Whether P. alstoni or some other member occurs in the mountains is unknown; it is possible a member of the P. leucomus group is absent from high altitudes on the peninsula, a pattern that would resemble that seen on Pegunungan Mekongga. The nature of the contact zones between the range of P. alstoni and those of P. leucomus to the north and P. topapuensis and P. weberi to the west are enigmas. Surveys in the east-central peninsula and through relevant regions in the central core of Sulawesi are needed to refine the geographic distribution of P. alstoni and its distributional pattern relative to the other three species.

A segment of P. alstoni's range matches that of the macaque, Macaca ochreata. That monkey has been recorded from the islands of Buton and Muna, and from the mainland of the southeastern peninsula north to the lakes region (Danau Towuti, Danau Mahatona, and Danau Matana). In landscapes north of the lakes in the east-central peninsula and the central core of Sulawesi, M. ochreata is replaced by M. tonkeana (Fooden, 1969; Groves, 2001, 2005). Prosciurillus alstoni also occurs on the islands and mainland south of the lakes region, but as opposed to Macaca ochreata, it ranges farther north into the east-central limb and to the northeastern portion of the central core.

Description

Prosciurillus alstoni is similar to P. leucomus in body size, with the tail averaging as long as, or only slightly shorter than, the length of head and body as in that species (length of head and body, 157–195 mm; length of hind foot, 40–48 mm; length of ear, 15–19 mm; weight, 135–210 g; see table 15). Thickness and color of the fur covering upperparts of head and body are also similar; both possess a uniformly thick (12–15 mm) coat that is dark brown flecked with black and orange along midline of the body from forehead to base of tail, but grading into brownish gray spotted with black and pale buff along sides of the head, body, forelegs, and hind legs. Dorsal surfaces of the front and hind feet may be the same color as the head and back, slightly darker, or slighter paler (buffy gray) in both species. Coloration of the body fur results from the mixture of dark gray curly underfur; longer overfur composed of black hairs, each blackish gray interrupted by a subterminal orange or pale buffy band and black tip; and black guard hairs barely projecting beyond the overhair layer. Cheeks range from buffy to ochraceous.

The dorsal background forming the upperparts of P. alstoni is interrupted by color patterning on the head and ears. Top and sides of the muzzle are ochraceous, a pattern also seen in P. leucomus. Unlike that species, however, P. alstoni lacks any sign of nape patches behind the ears—fur over the neck is indistinguishable in color from that covering the rest of the upperparts. Prosciurillus alstoni also lacks the prominent black ear tufts and ochraceous inner ear lining characteristic of P. leucomus. Instead, the hairs covering most of each ear on P. alstoni are similar in coloration to the head and body, a small black tuft sits at the inner dorsal margin of the ear, and from the medial surface springs a conspicuous white tuft that projects 5–8 mm beyond the dorsal curvature of the ear. The visual pattern evolves around an ear with a dab of black on the inner surface and rimmed by a white crest (see the color plates in figs. 10, 16). The white tufting is variable in expression both within and between samples; it is whitish buff in some specimens and absent from others. This variation is more fully explored in the sections discussing geographic variation and synonyms.

The short (5–7 mm thick) ventral coat of P. alstoni is deep, dark red—bordering on reddish brown or chestnut—on most specimens; some individuals from the southeastern peninsula have reddish orange or orange-red venters. The hairs forming the ventral covering are dark gray along their basal half and deeply pigmented with red or reddish orange along the distal half.

The tail of P. alstoni is equal to or slightly shorter than length of head and body (LT/LHB  =  89%–99%, see table 15) and is covered in long hairs, each patterned by alternating black and buffy or orange bands. The overall effect is rings of black and buff with buffy bands outlining margins of the tail and long black hairs forming a black terminal tuft. The ventral surface of the tail is reddish (paralleling the venter coloration) bordered by black and buffy margins. Overall coloration of the tail is closely similar to that seen in P. leucomus.

Females have three pairs of teats, one postaxillary pair, and two inguinal pairs. A single embryo was found in each of the few pregnant squirrels examined.

Views of the skull are illustrated in figures 12–Fig. 1314; cranial and dental measurements are summarized in tables 16 and 19.

TABLE 19

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Separate Population Samples of Prosciurillus leucomus and Prosciurillus alstoni Mean ± 1 SD and observed range (in parentheses) are listed.

Comparisons

Prosciurillus alstoni requires comparisons with P. leucomus, endemic to the northern peninsula north of the distribution of P. alstoni; P. weberi, known only by specimens from the lowlands fringing Teluk Bone west of the range of P. alstoni; and P. topapuensis, inhabiting the mountainous western portion of the central core to the west of P. alstoni.

Prosciurillus alstoni and P. leucomus: Both species are similar in body size and length of tail relative to length of head and body (table 15), in coloration of the fur covering head and body, legs, dorsal surfaces of front and hind feet, and color and patterning over the tail. Both share an ochraceous muzzle. Both show bright underparts but those of P. alstoni are typically more deeply pigmented, dark reddish brown as opposed to orange-red on average in P. leucomus (reddish orange to ochraceous is the chromatic range). Other pelage dissimilarities are striking (table 12): P. alstoni lacks any indication of nape patches behind the ears, a pattern characteristic of most examples of P. leucomus; and the ears are either adorned with a prominent white tuft or lack such a tuft in which case the ears, including the inner surfaces, are the same color as the head and neck—all specimens of P. leucomus exhibit prominent black ear tufts and bright ochraceous inner ear surfaces beneath the tufts.

The two species are not so different in cranial and dental dimensions (table 17) but significant proportional differences exist, which are reflected in the ordination of specimen scores projected onto first and second principal components extracted from principal-components analysis shown in figure 18. No marked separation among the scores into two discernable clusters exists along the first axis, where the spread is influenced by covariation in all of the dimensions measured except mastoid breadth and height of braincase; breadth of rostrum and lengths of nasals, rostrum, and diastema have somewhat more impact (table 20).

Fig. 21

Specimen scores representing population samples of Prosciurillus alstoni projected onto the first and second principal-components extracted from principal-components analysis. Symbols identifying samples are: filled circle  =  Pinedapa (N  =  19); filled triangle  =  Kuala Navusu and Sungai Tolewonu (N  =  32); cross  =  southeastern peninsula (Wawo, Masembo, Lalolei, Mowewe, Sungai Ahua; N  =  11); star  =  Mapane, lectotype of sarasinorum. Abbreviations: l  =  lectotype of mowewensis; p  =  paralectotype of mowewensis. See table 23 for correlations and percent variance.

TABLE 20

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus alstoni with Those of Prosciurillus leucomus Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 18.

The points separate into two overlapping clusters along the second component, reflecting the relatively slightly smaller skull, shorter tooth rows, but wider rostrum and longer diastema in P. alstoni compared to P. leucomus. These distinctions, while not immediately evident when comparing the descriptive statistics for each dimension in the two samples (tables 17, 19), can be appreciated visually by comparing side-to-side adult skulls with a comparable degree of wear on the teeth. Prosciurillus alstoni generally has a smaller skull and shorter tooth rows than P. leucomus.

Although the morphometric distinctions between the two species are subtle, the contrasts in color pattern are not. While not every example of P. alstoni has white ear tufts, none exhibits black ear tufts, and not one of the specimens we examined has nape patches behind the ears. These traits, along with their average darker red underparts and proportionately smaller skull and tooth rows, set P. alstoni apart from P. leucomus.

Prosciurillus alstoni and P. weberi: Our sample of P. weberi consists of eight individuals collected at two localities, with only five yielding a full set of cranial and dental measurements. If the two collection sites, in lowlands (100 m or less) fringing the northwestern margin of Teluk Bone, are representative of the altitude of P. weberi—namely tropical lowland evergreen rainforest habitats—then both P. weberi and P. alstoni share this lowland habitat affinity. The northern peninsular P. leucomus occurs through a range of forest formations from the coastal lowlands to montane habitats, and the west-central P. topapuensis inhabits mountain forests but in places ranges into lowlands.

Measurements of head and body, tail, hind feet, and ear from specimens of P. weberi are scanty but do indicate a close resemblance to P. alstoni, and other members of the P. leucomus group, in body size (tables 15, 16, and 17). Prosciurillus alstoni also closely resembles P. weberi in coloration of fur covering upperparts and underparts, as well as color and patterning on the tail. The striking differences between the two species involve markings on the back and ears. Although the background color of fur over the back is similar in both, that of P. weberi is broken by a “broad black band along the spine of the back, running from the neck, increasing in broadness in the middle of the back and diminishing towards the root of the tail,” as Jentink (1890: 116) described it. This dorsal pattern marks every specimen of P. weberi we studied but is absent from all examples of P. alstoni examined. Black tufts adorn the ears of P. weberi but comparable tufts in P. alstoni are white or not present (table 12). Jentink (1890: 116) noted that in one of the specimens of P. weberi he examined, “the black earpencils are slightly tipped with white.”

Our available samples from which we derived morphometric data for analyses are unsatisfactorily uneven: 63 skulls of P. alstoni but only five from P. weberi. Results we present here must be tested by employing a larger sample of P. weberi. Mean values for most cranial dimensions in the sample of P. weberi are smaller than comparable dimensions in the larger sample of P. alstoni (table 17). These distinctions are transformed visually in the ordination showing specimen scores projected onto the first and second principal components extracted from principal-components analysis in figure 19. There the large cloud of scores representing P. alstoni overlaps the smaller group of points for P. weberi. Covariation in all cranial and dental dimensions except height of braincase contributed to the spread of scores along the first principal component (table 21). The center of the larger constellation of points lies to the right of the smaller cluster, reflecting the overall average greater cranial and dental dimensions of P. alstoni compared to P. weberi.

Fig. 22

The habitat of Prosciurillus alstoni in tropical lowland evergreen rain forest on flat terrain near Musser's camp at Kuala Navusu, 30 m. The large tree is Dracontomelon dao, which emerges above the upper canopy layer, is scattered on flats and lower slopes of ridges, and is one of the largest trees in the forest. The tree photographed is about 150 ft high, 4 ft diameter just above the buttresses, and 10 ft across the bases of the buttresses. The tree squirrels Rubrisciurus rubriventer and Prosciurillus murinus were trapped in the same forest. Range of ambient temperatures recorded during the sampling period is listed in table 2. Photographed in 1975.

TABLE 21

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus alstoni with the Sample of Prosciurillus weberi Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 19.

The scatter along the second principal component results in separation of the specimen scores for P. weberi from the larger cloud formed by the sample of P. alstoni, and is a measure of distinctions in cranial and dental proportions. Highlighted is the relatively narrower skull and interorbital region of P. weberi compared with P. alstoni, its relatively shorter nasals and rostrum, lower braincase, smaller bullae, and shorter tooth row, but wider rostrum and longer diastema and postpalatal region (table 21). Mean skull length is not so different in the two species (table 17), but many of the internal dimensions are less for P. weberi relative to those dimensions in skulls of P. alstoni, especially interorbital breadth and toothrow length, and three internal dimensions are of relatively greater magnitude.

Prosciurillus alstoni and P. topapuensis: These two species are dissimilar in altitudinal distributions, coat color and patterning, and cranial proportions. Prosciurillus alstoni inhabits tropical lowland evergreen rain forests and has not been collected above 1200 m within its range, which is east of the distribution for P. topapuensis (see map in fig. 11). That species is endemic to the western mountains and foothills of central Sulawesi and ranges through a variety of old-growth forest habitats, from tropical lowland evergreen rain forest to upper montane rain forest (table 4).

The species resemble each other in physical size with the exception that across geographic samples, P. topapuensis typically has a tail that is absolutely shorter and shorter relative to head and body length, and larger ears (tables 15, 16). Most P. topapuensis have thicker fur, especially samples from high altitudes; the dorsal coat of specimens from low altitudes is inseparable in color from upperparts of P. alstoni, but individuals from higher altitudes show a duller fur: the colored bands are mostly buffy instead of orange and buff. Tails of the two are similar in coloration and pattern of hair bands.

The striking dissimilarities between the two species involve the underparts and ears. All examples of P. topapuensis we examined have dark gray underparts lightly washed with buffy or ochraceous hues, or tinted silver, which contrasts strikingly with the dark reddish to reddish brown venters so characteristic of P. alstoni. Black tufts mark the ears on P. topapuensis. These are not as prominent as seen in some samples of the northern peninsular P. leucomus, and the variation in expression ranges from conspicuous tufts to just a trace of black so the ears are covered with the same color fur as the head and neck. No example of P. topapuensis has white ear tufts, which is usual in P. alstoni (table 12).

Skulls of the two species are similar in overall size and in many internal cranial dimensions but differ in dimensional proportions. The correspondence in size is indicated by the mean values listed in table 17 and reflected in the graph of specimen scores projected onto first and second principal components extracted from principal-components analysis shown in figure 20. No separation of scores into discrete clusters is evident along the first component where all but two variables load positively (height of braincase and length of tooth row are the exceptions) and contribute to the the spread of points. Fewer variables load strongly along the second principal component but they point to significant differences in shape between the two species (table 22). Compared with P. topapuensis, the skull of P. alstoni is relatively wider (as indexed by zygomatic, interorbital, and mastoid breadths) and the orbit and ectotympanic bullae relatively longer; the nasals, diastema, and tooth row are relatively shorter, and the rostrum narrower.

Fig. 23

Hillside forest near Kuala Navusu, 60 m. Aminudi is touching an Artocarpus sericarpus, one of the breadfruit species that is scattered through the forest on streamside terraces and lower margins of hillsides. The forest on hills tends to be shorter than the tall forest on the flats. The palm in the center of the photograph, Licuala rumphii, is common in the understory. Examples of Prosciurillus alstoni, P. murinus, and Rubrisciurus rubriventer were trapped here. Photographed in 1975.

TABLE 22

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus alstoni with Those of Prosciurillus topapuensis Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 20.

Geographic Variation

Specimens of P. alstoni generally look alike no matter where they were obtained throughout the geographic range of the species as indicated by our samples at hand (tables 14, 19). The notable variation we see among adults involves the ear region. Ears of the nine specimens in the type series of tonkeanus from Tonkean on the east-central peninsula of Sulawesi (see gazetteer and fig. 11) have only short buffy hairs fringing their margins (clearly rendered in Meyer's, 1896, plate [reproduced in fig. 9] and evident in the color images of the type series given to us by Clara Stefen) and lack the characteristic white ear tufts seen in samples elsewhere within the range of P. alstoni; backs of the ears are covered with dark buffy hairs, which reach the rim of the pinna but do not project beyond it to form a tuft in most specimens, and form a short tuft in others. Otherwise, color of the upperparts, underparts, and tail of individuals in the Tonkean series match our samples from the central core of the island and the southeastern peninsula. No other samples of the squirrel have been collected from the east-central peninsula so we do not know whether the absence of white tufts is fixed in the population there, is individually variable at other localities, or if presence or absence of the white tufts shows a geographic pattern over the peninsula.

Our samples of P. alstoni elsewhere within its range exhibit variation in frequency of ear tufts and slight variation in color. In the central core of the range, three of the 24 skins from Kuala Navusu have short, inconspicuous whitish buff or buffy white tufts. Backs of the ears are covered with buffy white hairs that project 1–2 mm beyond the ear rims. The remaining specimens support a white coat over the medial surface of each ear, and the white hairs project from 3 mm to 8 mm beyond the ear rim. Individuals with the longer tufts match Anderson's color plate of alstoni (fig. 16) and Meyer's portrait of sarasinorum (fig. 10). One of the 12 skins from Sungai Tolewonu exhibits an inconspicuous, short buffy white tuft—nearly a fringe—but the others sport white tufts, the range in length comparable to that of the sample from Kuala Navusu. Of the 23 specimens from the southeastern peninsula (Wawo, Masembo, and Lalolei), one lacks tufts, back of the ears are dark buff with the hairs forming a low buffy fringe on the rim of the pinna (closely similar to the type series of tonkeanus); backs of the ears are buffy in seven individuals, with the hairs projecting 2 mm beyond to form an inconspicuous, short buffy tuft or high fringe; 18 specimens have prominent white tufts, the range in length comparable to that of the samples from Kuala Navusu and Sungai Tolewonu.

Two adult skins and skulls (MZB 6250 and 6251) from Pulau Buton are insular examples of P. alstoni (if Buton is the actual provenance) and were discussed by Sody (1949: 107) under “Callosciurus tonkeanus.” Musser examined and compared the pair with AMNH specimens of P. alstoni collected at several places (Wawo, Masambo, and Lalolei) on the southeastern peninsula. In size and configuration of the skull, body size and proportions of appendages, and general coloration of fur covering body and tail, the two squirrels from Buton are similar to samples of P. alstoni from the mainland of the southeastern peninsula, and differ only in expression of the ear tufts. Instead of showing the tall and conspicuous tufting seen in most P. alstoni, the two individuals from Buton have less prominent tufts and they are white tinged with buff, matching some specimens from the central core and southeastern peninsular mainland described above. AMNH 101327, for example, from Lalolei, on the mainland, has short, whitish buff ear tufts; in this aspect and overall pelage color and patterning, the specimen is indistinguishable from the two Buton squirrels—although collected from different places at different times, all three squirrels could have been part of the same litter.

Multivariate analyses of cranial and dental variables among our geographic samples (identified in table 1) of P. alstoni drawn from the eastern section of Sulawesi's central core and the southeastern peninsula do not identify geographic components of the variation in these variables. The scatter of specimen scores projected onto first and second principal components extracted from principal-components analysis shown in figure 21 forms one large cloud in which are intermingled the points representing squirrels in the three geographic population samples. In addition to not revealing significant internal structure that correlates with geographic origin of the samples, the ordination also expresses individual variation within an age class, and variation associated with age since the range from young adults to old adults comprise each sample. Covariation in most cranial variables contributed to the spread of scores along the first axis (size), fewer load heavily on the second component (shape; table 23). Missing from this analysis is the sample from Tonkean, which consists of skins only.

Fig. 24

Specimen scores representing population samples of Prosciurillus topapuensis from the central core of the island (empty triangle, N  =  50) and P. leucomus from the northern peninsula (filled diamond, N  =  26) projected onto the first and second principal-components extracted from principal-components analysis. The ellipses outline 95% confidence limits for the specimen scores forming each cluster. Equations for the regression lines are: P. leucomus, Y  =  0.621X−0.120 (F  =  22.07, P  =  <0.01); P. topapuensis, Y  =  0.222X+0.038 (F  =  9.25, P  =  <0.01). The Y-intercepts of each regression line of the second principal component on the first component are significantly different (−0.120 versus +0.038; F  =  28.31, P  =  <0.001). See table 27 for correlations and percent variance.

TABLE 23

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus alstoni Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 21.

Ecology

Prosciurillus alstoni inhabits the upper canopy of primary tropical lowland evergreen rain forests, traveling through this layer along the pathways formed by the interlaced branches and woody vines. At gaps in the canopy squirrels descend to the ground where they bound along tree trunks and limbs lying on the forest floor and cross streams and rivers on bridges formed by branches of live trees arching over the water as well as rotting tree and palm trunks and tree limbs connecting opposite stream terraces. Most of the specimens Musser collected at the Kuala Navusu and Sungai Tolewonu areas were trapped on limbs of live trees growing over water or on rotting trunks and treefalls bridging streams (see summary of habitats at trapping sites in table 24, and photographs of forest in figs. 8, 22, and 23).

Fig. 25

Specimen scores representing population samples of Prosciurillus topapuensis and P. weberi (star, N  =  5) projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples of P. topapuensis are: filled circle  =  Rano Rano (N  =  11); x  =  Besoa-Lindu trail (N  =  5); cross  =  Gunung Lehio (N  =  9); filled upright triangle  =  Gunung Kanino (N  =  5); filled inverted triangle  =  Sungai Miu and Sungai Sadaunta (N  =  9); filled left-pointing triangle  =  Pegunungan Latimojong (N  =  11). Arrow identifies score for the lectotype of weberi. See table 28 for correlations and percent variance.

Fig. 26

Specimen scores representing six population samples of Prosciurillus topapuensis projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples are: filled circle  =  Rano Rano (N  =  11); x  =  Besoa-Lindu trail (N  =  5); cross  =  Gunung Lehio (N  =  9); filled upright triangle  =  Gunung Kanino (N  =  5); filled inverted triangle  =  Sungai Miu and Sungai Sadaunta (N  =  9); filled left-pointing triangle  =  Pegunungan Latimojong (N  =  11). A: All cranial and dental variables are represented, but holotypes of topapuensis and hirsutus are excluded. See table 29 for correlations and percent variance. B: Includes the holotypes of topapuensis (“t” and filled square) and hirsutus (“h” and filled right-pointing triangle) but because these specimens are damaged only 11 cranial and dental variables could be employed. See table 30 for correlations and percent variance.

TABLE 24

Summary of Habitat at Trapping Sites, Stomach Contents, and Other Relevant Information for Specimens of Prosciurillus alstoni Collected by Musser in Central Sulawesi, 1975–1976 Collection locality, specimen number, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). The two collection localities (Kuala Navusu and Sungai Tolewonu) are in tropical lowland evergreen rain forest. All squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

While trapping records indicate P. alstoni to be common in the region where Musser worked, he rarely saw the squirrels; they were quiet and wary compared with the P. topapuensis (see that account) he encountered. Occasionally squirrels were seen traveling through the upper canopy and sometimes dashing along tops of rotting treefalls on the ground in forested ridgetops, hillsides, and stream terraces. Calls heard were similar to those vocalizations of P. topapuensis. So too were the factors eliciting alarm calls: approaching rain, human sounds, and diurnal avian predators.

Contents of somachs indicate that soft fruits and insects comprise the diet (table 24). Remains of figs were the most common fruit found in stomachs. In addition to remains of fruit, several stomachs contained a variety of insects, most of which would be encountered in tree crowns (table 57). Macrolepidopteran larvae (caterpillars) feed on foliage and, judged by the large numbers in stomachs, were actively gleaned from leaf surfaces by the squirrels. Larvae of buprestid beetles live beneath the bark of standing trees and are dug out. Along with fruit, arboreal termitid termites were in two stomachs, one with about two dozen workers and soldiers, but the other packed with these insects. The squirrels had located and scratched open a nest adhering to a limb in the tree crown either before or after eating fruit. Adult beetles and beetle larvae other than buprestids, as well as the occasional ant are also picked off surfaces of leaves and bark. The few ant pupae found in stomachs were likely dug out of a nest.

Ectoparasites

The only record is the sucking louse Hoplopleura alstoni, n. sp. (table 56), that we describe in a following section; this species of louse is unique to its host.

Sympatry

The range of P. alstoni on the central core and southeastern peninsula of mainland Sulawesi overlaps distributions of P. murinus, Rubrisciurus rubriventer, and the ground squirrel, Hyosciurus ileile (table 6). In the lowlands behind Kuala Navusu and Sungai Tolewonu at the northern section of the central core of Sulawesi, Musser trapped P. alstoni in the same traplines where he encountered the other three species, and sometimes in the same traps (table 24).

Synonyms

Four scientific names represent samples of P. alstoni. Information covering their type specimens and reasons behind their allocations is summarized below.

Sciurus tonkeanus Meyer, 1896: 25, plate X, figure 4. LECTOTYPE: SNSD B3178 (skin mounted in a live pose, without a skull), an unsexed adult purchased from Charles Cursham in 1889. TYPE LOCALITY: Indonesia, Propinsi Sulawesi Tengah, east-central peninsula of Sulawesi, Tonkean (near Sinorang), 01°24′S, 122°30′E, on the coastal plain, 0–100 m (locality 5 in gazetteer and on map in figure 11).

Feiler (1999: 407) identified SNSD B3178 as the “holotype” and eight additional specimens as “paratypes.” Meyer (1896: 25) had before him an unspecified number of flat skins without skulls and postcranial skeletons (“platte Felle ohne Knochen”) when he named and diagnosed tonkeanus and did not designate a holotype, the usual practice at the time. Feiler's indication therefore has made SNSD B3178 the lectotype of Sciurus tonkeanus Meyer, 1896, the other eight specimens being paralectotypes, designations in agreement with Article 74.5 in the Code (ICZN, 1999: 82–83): “In a lectotype designation made before 2000, either the term ‘lectotype,’ or an exact translation or equivalent expression (e.g. ‘the type’), must have been used or the author must have unambiguously selected a particular syntype to act as the unique name-bearing type of the taxon. …” By using the term “holotype” (an “equivalent expression (e.g. ‘the type’),” Feiler has “unambiguously selected a particular syntype to act as the unique name-bearing type of the taxon.”

The eight paralectotypes (SNSD 3179–86) are unsexed and without skulls. All are unstuffed pelts that “seem to have dried in the position they just happened to be in and were not prepared ‘properly’ … the ears are all flat or broken and the tails bent or lost.” (C. Stefen, in litt., 2008).

Clara Stefen kindly sent us color images of the lectotype and paralectotypes, and based upon them, along with Meyer's (1896) description and color plate (fig. 9), we can write that tonkeanus closely resembles the holotypes of sarasinorum (fig. 10) and alstoni (fig. 16) in coloration of the fur covering body and tail, differing only in color of the ears and expression of tufts (see appendix 3 for Meyer's description in the original German). The white covering on the medial surface of each ear that extends beyond the margin of the pinna to form a conspicuous white tuft that is so characteristic of most examples of P. alstoni is absent from the sample of tonkeanus. Instead, outer and inner surfaces of the ears are dark brown or buffy, and these hairs project slightly beyond the margin of the pinna to form a short and inconspicuous fringe in most specimens, and a short tuft in others. We don't know if color and size of the ear fringe seen in the sample from Tonkean are characteristic of populations inhabiting all forests on the east-central peninsula, for no other samples have been collected in that region. We do know that the tonkeanus ear pattern is present at a low frequency in our samples from the central core and southeastern peninsula (see discussion in the section covering geographic variation); these specimens closely resemble the condition in the lectotype and paralectotypes of tonkeanus, as shown in Meyer's plate (fig. 9) and the color images provided by Clara Stefen.

More samples of tree squirrels from the east-central arm of Sulawesi, especially in the region near the central core, are required to assess the actual range of variation in color and size of the ear tufting in those populations. Although we are currently ignorant of the variation in cranial and dental dimensions among populations on the east-central arm, we suspect the ranges of those dimensions would not be significantly different than those we have uncovered here for our samples from the central core and southeastern peninsula (table 19), but only through study of new material from the east-central peninsula can our assumption be tested. Until then we regard the sample of tonkeanus to represent a population of Prosciurillus alstoni in which the ears have buffy fringes and lack white ear tufts, at least in the type series, the only sample currently available for study.

Sciurus sarasinorum Meyer, 1898: 1 (1899: 21, pl. V). LECTOTYPE: SNSD B3826 (skin and skull; measurements are listed in table 14), an adult male collected during February 1895, by Fritz and Paul Sarasin. TYPE LOCALITY: Indonesia, Propinsi Sulawesi Tengah (northern portion of the central core), Mapane, 01°26′S, 120°40′E, near sea level at the southern margin of Teluk Tomini (locality 4 in gazetteer and on map in figure 11).

Clara Stefen sent us color photographs of the skin and skull of the specimen collected at Mapane—and we also have in front of us prints of the skull derived from negatives made by G.H.H. Tate in 1951 during his visits to European museums. An unstuffed pelt dried in a distorted shape forms the skin. All appendages (ears, feet, and tail) are intact, and color of the fur is similar to that depicted in Meyer's color plate (1899; reproduced in fig. 10); the white ear tufts are conspicuous. The color hues of the pelt have retained the vibrant integrity of the live squirrel, even after 113 years. In color of upperparts, underparts, tail, ears, and extent of white ear tufts, the skin of SNSD B3826 is inseparable from H.C. Raven's sample collected in the 1920s from Pinedapa, southeast of Mapane, Musser's specimens collected in the 1970s from the Malakosa region northwest of Mapane (see map in fig. 17) and from G. Heinrich's samples collected in the 1930s from the southeastern peninsula. Except that the hues are paler in Anderson's (1879) color plate of “Sciurus alstoni” (see fig. 16), in particular the underside being much less brightly colored, that portrait bears a striking resemblance to the squirrels from Mapane and Usu portrayed as sarasinorum in Meyer's color plate (see fig. 10), a population identity reinforced by their shared white and prominent ear tufts.

The skull of SNSD B3826 is intact except for a slight separation between the interparietal and occipital region, and a hole in the bony palate and one on top of the skull behind the nasals, which traces the path of a shotgun pellet. The left dentary is whole but the posterior ramus of the right dentary is in fragments, the anterior portion undamaged. Values from cranial and dental dimensions of the holotype fall within the range of variation of our samples that share similar fur coloration and patterning. In the ordination of specimen scores for population samples (identified in table 1) from the Malakosa region, Pinedapa, and the southeastern peninsula projected onto the first and second principal components extracted from principal-components analysis, the score for the holotype of sarasinorum clusters with scores representing specimens from those three geographic regions (fig. 21).

Meyer (1898: 1) based his description of sarasinorum on two specimens collected by the Sarasins and, as was the custom then, did not designate either as the holotype. One was collected at Usu (“Oesoe” on old maps; also spelled “Ussu”), 02°36′S, 121°06′E, near sea level at the northern end of Teluk Bone on February 18, 1896; the other was obtained farther north at Mapane on the south coast of Teluk Tomini in February 1895. Both specimens are represented by live poses in Meyer's (1899, pl. 5) color plate (reproduced here in fig. 10). Meyer (1899: 21) noted that the bottom pose represents the individual from Usu and was rendered natural size, while the top pose, which is one-half natural size, was drawn from the animal collected at Mapane. Both individuals have prominent white ear tufts, and are closely similar in color and patterning of the fur over body and tail.

Identifying the type locality and type specimen for sarasinorum is puzzling for anyone checking the published literature up to the late 1990s. Ellerman's (1940: 375) classic compendium on families and genera of living rodents noted only “Central Celebes” as the source of the two specimens. More than a decade later, in their checklist of land mammals of New Guinea, Celebes, and adjacent islands, Laurie and Hill (1954: 93) simply referred to both locations in their indication of a type locality: “Ussu, northern end of Gulf of Boni, and Mapane, southern end of Gulf of Tomini, Celebes.” By the early 1990s, Corbet and Hill (1992: 304) had stated the type locality to be “Ussu, N end of Gulf of Boni, Sulawesi,” which would imply that they regarded the specimen from Usu to be the type.

Neither Usu nor the specimen collected there in 1896 were listed in Feiler's (1999: 407) accounts of type specimens housed in the collection of the Staatliches Museum für Tierkunde at Dresden. He identified as “holotype” the specimen from Mapane, and that place as the type locality. No reference was made to a specimen from Usu. Perplexed, we inquired of Clara Stefen if the squirrel from Usu was still in the collection at Dresden, and she (in litt., 2008) wrote “I can't find any hint of it; it's not in the collection, but [I] did not even see an entry on the relevant systematic index card which seems odd to me, as they [the cards] probably were started under the directorship of Meyer.”

We subsequently located the squirrel from Usu in the collection at the Naturhistorisches Museum Basel. In the mammalogy archives at AMNH we found a photograph of a skull from Usu taken by George H.H. Tate when he visited Basel in 1951. Our contact at Basel, Loïc Costeur, informed us that the specimen is listed in the museum's database; he subsequently found it in the collection, and sent us color images of the skin and skull. The adult skin (NMB 1199), prepared as a stuffed museum study specimen, is intact except for the head where large patches of skin are missing on the right and left side. The animal was clearly shot in the head and this damage is reflected in the skull (NMB 8080). The anterior half is intact and all teeth are present but all that remains of the posterior half is the roof of the braincase and cracked basicranial region still retaining the auditory bullae; the mandible is complete. The specimen was collected by Fritz and Paul Sarasin, and is one of the two studied by Meyer (1898, 1899). The specimen from Mapane, which Feiler identified as the “holotype,” has by that action become the lectotype of Sciurus sarasinorum Meyer, 1898 (see Article 74.5 in ICZN, 1999: 82–83), the specimen from Usu being the paralectotype. The two specimens, although from widely separate localities, are closely similar in body size and coloration of fur. They in turn are inseparable from our samples collected in the Malakosa region, Pinedapa, and the southeastern peninsula.

Sciurus mowewensis Roux, 1910: 519. LECTOTYPE: NMB 1626 (skin) and 4243 (skull), an adult female collected on February 23, 1903, by Fritz and Paul Sarasin. Measurements are listed in table 14. TYPE LOCALITY: Indonesia, Propinsi Sulawesi Tenggara (southeastern peninsula of Sulawesi), Mowewe, 04°10′S, 121°52′E, approximately 500 m (locality 8 in gazetteer and on map in figure 11).

Roux based his description of mowewensis on an adult female (NMB 1626/4243) from Mowewe and an adult male (NMB 1627/4244) from nearby “Ahua River [ =  Sungai Ahua],” and compared them most closely with sarasinorum, known at the time only from the two specimens described by Meyer (1898, 1899). Roux's description (translated from the original in German; the German text is reproduced in appendix 5):

Roux basically redescribed sarasinorum, which was detected by Moore (1958: 2): “Inspection of the Archbold material [at AMNH], Roux's (1910, p. 519) description, and Meyer's (1899, p. 5) colored plate of sarasinorum shows that Roux's squirrel is an obvious synonym of sarasinorum.” This attribution is reinforced by our inspection of the color images of the lectotype and paralectotype (these designations were made by someone at Basel and entered into their unpublished catalog of type specimens, according to Loïc Costeur, who examined the specimens for us; Roux had not identified either specimen as the holotype) sent to us by Loïc Costeur. Following this manuscript catalog, we hereby formally designate NMB 1626/4243 the lectotype of Sciurus mowewensis Roux, 1910, the other specimen (NMB 1627/4244) being the paralectotype. Each skin is prepared as a dry and stretched pelt; color of the fur is still bright and unaltered. The pattern of color on the body and tail, along with their prominent white ear tufts, identifies the specimens as sarasinorum, and in turn as examples of the older name, alstoni, and not something uniquely distinct.

Values for cranial and dental dimensions measured fall within the range of variation for our samples of P. alstoni from the Malakosa region, Pinedapa, and the southeastern peninsula (table 19). Except for missing second molars and a missing third premolar from the holotype, both skulls are intact, as can be seen from the photographs taken by G.H.H. Tate in 1951 (stored in the mammalogy archives at AMNH). Loïc Costeur measured both skulls for us. His values, along with those from the holotype of sarasinorum and our samples from central Sulawesi and the southwestern arm, became the subjects of principal-components analysis, which resulted in the ordination depicted in figure 21. The scores for the types of mowewensis cluster with points representing specimens from Pinedapa and the Malakosa region; the score for the holotype of sarasinorum is nearby. Scores denoting the AMNH specimens from the southeastern peninsula are scattered throughout the cluster derived from the samples from the Malakosa region and Pinedapa. There is no evidence from cranial and dental dimensions or proportions derived from the two skulls of mowewensis indicating they are anything other than another sample of sarasinorum, which identifies a population for which P. alstoni is the oldest name.

Sciurus elbertae Schwarz, 1911: 639. HOLOTYPE: SMF 721 (a skin and skull were described by Schwarz; the skull is present in the Senckenberg Museum but the skin is missing [G. Storch, in litt., 2008]; measurements are listed in table 14), an unsexed adult collected by J. Elbert (original number 227). TYPE LOCALITY: Indonesia, Propinsi Sulawesi Tenggara (southeastern peninsula and offshore islands of Sulawesi), Eempuhu, Pulau Kabaena (05°15′S, 121°55′E), off the coast of the southeast peninsula (see map in figure 11). Schwarz identified the type locality as “Eempuhu, East Kabaëna.” No elevation is attached to the specimen. Highlands constitute most of the island with topographic relief ranging from sea level to 1570 m.

Schwarz (1911: 639) examined two specimens, each consisting of a skin and skull, and regarded them to be “A pale-coloured member of the Sciurus leucomus-group.” Judged from his description, the fur of elbertae is somewhat paler than the rich and darker hues typical of sarasinorum from the mainland. No reference to ear tufts were made, only that the general color of the upperparts was brownish (between “olive” and “raw umber”) “with a creamy-buff tinge on head.” We have not seen a “creamy-buff tinge” on the head of any specimen of P. alstoni, or any other specimen in the P. leucomus group. Unfortunately, both skins are missing from the collection at Senckenberg so we cannot determine if Schwarz was actually describing “creamy-buff” ear tufts, which would make sense. Both specimens from adjacent Pulau Buton have whitish buff ear tufts (see discussion of geographic variation).

The skull of the holotype (SMF 721) is complete except for broken basicranial and occipital regions; all premolars and molars are fully erupted and show moderate wear. The skull of the paratype (SMF 4878), slightly damaged, is that of a juvenile (G. Storch, in litt., 2008). Values for the cranial and dental dimensions that could be measured (by G. Storch) are listed in table 14. Some dimensions are smaller in the skull of elbertae compared with samples of species in the P. leucomus group (contrast tables 13 and 19); values for interorbital breadth, and lengths of nasals, rostrum, diastema, and bony palate, for example, are less than the range of values for these variables in the sample of P. alstoni. Length of PM4–M3 (7.3 mm) is within the range of variation for most of our samples of the P. leucomus group, which suggests to us that although all teeth are erupted and moderately worn, the skull of SMF 721 may be from a very young adult. Currently, we cannot assess the significance of the mensural differences described here without a larger sample from Pulau Kabaena containing a range of ages, from very young to old adults.

Schwarz compared elbertae with the skull of what he identified as “Sciurus mowewensis” collected on Pulau Buton. Among the distinctions he noted (primarily some smaller dimensions of elbertae) was the presence of a distinct medial spine extending from the posterior margin of the bony palate in elbertae and its absence in the Buton specimen. Among our samples of P. alstoni (of which mowewensis is a synonym), the posterior margin of the bony palate exhibits three variants: a straight edge, a margin interrupted by a median bony nubbin, or “a distinct median spine” marking the edge.

On our copy of the published description where Schwarz indicated elbertae to be a member of the “Sciurus leucomus-group,” G.H.H. Tate had crossed out “leucomus” and scribbled “nigrovittatus or notatus” in the margin. We had also considered these possible identifications but rejected them. Ranges of both species cover primarily peninsular Thailand and Malaya, and islands on the Sunda Shelf. Callosciurus nigrovittatus is recorded from peninsular Thailand, the Malay Peninsula, Sumatra and Java, and the small islands of Tioman and Saddle on the Sunda Shelf (Corbet and Hill, 1992: 292). This squirrel is larger-bodied than Schwarz's elbertae. Schwarz, for example, recorded length of the “upper tooth row” (PM3–M3) as 7.9 mm, which is well outside the observed range of values (minimum, 8.3–9.2 mm; maximum, 9.0–9.7 mm; N  =  93) given by Sody (1949: 95) for 17 samples from Java, the island supporting populations of C. nigrovittatus closest to Sulawesi. Callosciurus nigrovitattus has gray underparts and prominent white and buffy parallel stripes on sides of the body (see color pl. 7 in Medway, 1969, and pl. III in Askins, 1988), ventral coloration and body patterning unlike elbertae or any other kind of squirrel known from Sulawesi.

Callosciurus notatus has a broader geographic range than C. nigrovitattus, and is found on peninsular Thailand and Malaya; the larger Sundanese islands of Sumatra, Java, and Borneo; many smaller islands on the Sunda Shelf; east to Pulau Lombok in the Lesser Sunda Islands; and on Pulau Salayar, just south of the southwestern peninsula of Sulawesi (Corbet and Hill, 1992: 291). Sody (1949: 82) published observed ranges for length of upper tooth row derived from 17 samples of C. notatus from Java (minimum, 8.4–9.6; maximum, 8.6–10.3 mm; N  =  92) and for five specimens from Pulau Salayar, off the southern coast of Sulawesi's southwestern peninsula (minimum, 9.3 mm; maximum, 9.7 mm), illustrating a range much greater than the value of 7.9 mm for the holotype of elbertae. Callosciurus notatus resembles C. nigrovitattus in having parallel buffy and white stripes on each side of the body; the populations on Java have either gray or buffy underparts and specimens from Pulau Salayar have dull buffy venters (see the color plates in Medway, 1969, and Askins, 1988; pl. 25 in Payne et al., 1985; Corbet and Hill, 1991: 292). The two examples of elbertae are not examples of either C. nigovitattus or C. notatus.

Prosciurillus weberi (Jentink, 1890)

Sciurus weberi Jentink, 1890: 115, pl. VIII, pl. X figs. 1–3.

Lectotype and Type Locality

The lectotype of Prosciurillus weberi is an adult female (RMNH 13342) collected by Max Weber in February of 1889. A mounted skin and accompanying skeleton comprise the specimen. The skull is intact. Measurements are listed in table 13. Jentink (1890: 115) had “three adult skins, two skeletons and one skull” at hand when he described weberi, and with the aid of Chris Smeenk at Leiden, Wim Bergmans at Amsterdam, and Paula Jenkins at London, we have located all the elements that are the basis for Jentink's description. Only RMNH 13342 remains at Leiden, and following Chris Smeenk's suggestion (in litt., 2008), we select it as lectotype, following Article 74.1 of the Code (ICZN, 1999: 82). One of Weber's specimens is now in the collection at the Natural History Museum in London (BMNH 94.7.4.6, a skin only), which becomes a paralectotype. Two of Weber's other specimens are in the collection at the Zoological Museum, Amsterdam: ZMA 11.327, a mounted skeleton (including skull) and ZMA 11.328, a mounted skin and skull; both are paralectotypes. (Chris Smeenk wrote us that in 2010, the Amsterdam collections will be moved to Leiden and become incorporated into the Leiden collections; the catalogue numbers will remain unchanged and preceeded by ZMA.)

The type locality is Palopo (“near Palopo” is indicated on some tags), 03°01′S/120°13′E, 0–100 m (locality 2 in the gazetteer and figure 11) in the southern lowlands of the central core of Sulawesi, Propinsi Sulawesi Selatan, Indonesia. Jentink (1890: 115) gave “Luwu near Palopo, central Celebes” as the type locality; Luwu is the administrative district containing Palopo.

Emended Diagnosis

As in most of the other members of the Prosciurillus leucomus group, P. weberi has a moderate-size body and a tail equal to or shorter than length of the head and body. It contrasts with the other four species by the following combination of pelage traits (see table 12): (1) dorsomedial surface of each ear covered with long black hairs projecting beyond ear rim to form a prominent tuft; (2) no bright ochraceous hairs lining inside of the pinnae, which is the same color as the fur on neck and head; (3) no nape patches behind the ears; (4) prominent middorsal black stripe extending along back from neck to base of tail (5) reddish orange underparts; and (6) currently known only from lowlands fringing the northwestern margin of Teluk Bone.

Geographic and Altitudinal Distributions

Records of P. weberi are represented only by the voucher specimens collected between 1889 and 1940 near Masamba and Palopo in lowlands fringing the central mountains to the west and Teluk Bone to the east in the southeastern margin of Sulawesi's central core (see gazetteer and map in figure 11). These sites are no higher than 100 m.

The known range of P. weberi is allopatric to those of two other members in the P. leucomus group. To the east, P. alstoni occurs primarily in lowland forest habitats in the eastern portion of the central core, the east-central peninsula, the southeastern peninsula, and has been collected from two islands (see map in fig. 11). Usu, in the coastal lowlands fringing the southwestern end of Teluk Bone, is the collection locality for P. alstoni closest to Masamba, which is about 80 km to the west of Usu. See the account of P. alstoni for an expanded discussion contrasting the geographic ranges of the two species.

Prosciurillus topapuensis inhabits forests in the mountains to the west of Masamba and Palopo (see map in fig. 11). No specimens have been collected lower than 350 m and no collection localities are close to the range of P. weberi. Surveys in the foothills west of Masamba and Palopo, provided that intact forest is present, are required to determine the distributional relationships between the two species. Here P. weberi may be restricted to lowland tropical evergreen rain forest and P. topapuensis to montane forest habitats.

The actual geographic distribution of P. weberi is unknown. If it is restricted to tropical lowland rain-forest habitats, the species may occur all along the eastern coast of the central core, westward through the northern part of the Tempe Depression along the margin of the mountains, and north along the western coast possibly to the Palu area—the range would fringe the west-central foothill and mountain distribution of P. topapuensis. No samples of squirrels are available from these lowlands and no place along those coasts or in the Tempe Depression has been carefully surveyed for small mammals. Much of the southern part of this lowland fringe has been deforested (see maps in Whitten et al., 1987: 102, and Supriatna et al., 1992: 37), so we may never know what member of the P. leucomus group inhabited the orginal forest cover.

In the past, P. weberi may have ranged across the Tempe Depression south throughout lowlands of the southern part of the southwestern peninsula. No modern specimens of the P. leucomus group have been collected in that region, but at least one once occurred there. A subfossil mandibular fragment collected from a cave in the Maros region attests to the former presence of a tree squirrel, possibly representing P. weberi (see the account of Prosciurillus sp.). Tree squirrels may still exist in the small patches of lowland forest remaining on the southern part of the peninsula, but most of the region is densely populated agricultural land (see the maps in Whitten et al., 1987: 102, and Supriatna et al., 1992: 37).

Our experience with nonvolant endemic Sulawesi mammal distributions indicates that the range of P. weberi is unusual. As currently documented by voucher specimens, its range is not congruent with any other endemic mammal, a pattern contrasting with many of the distributions shared by species in other mammal groups. This discordance suggests to us that either the range of P. weberi will prove to be greater than what is now represented by specimens (as we outlined above) or that it once occurred on the southwestern peninsula but is now extinct (and possibly represented by the subfossil from the Maros region).

A young adult Prosciurillus weberi in MZB (6255) bears a skin tag indicating it was collected in 1908 from “Menado” (see also Sody, 1949: 107), but was certainly mislabeled. Prosciurillus leucomus is the only member of the P. leucomus group that has ever been collected from the Manado region (see gazetteer for P. leucomus).

Description

“This beautiful Squirrel,” wrote Jentink (1890: 115–116) of weberi,

In its physical size and proportions of feet and tail, P. weberi closely resembles P. alstoni (table 15). Dark brown upperparts sprinkled with orange and black, along with dark reddish or reddish orange underparts, are also common to both species. The combination of prominent black ear tufts and black middorsal stripe, however, is unique to P. weberi, and is illustrated in Jentink's (1890) color plate of weberi posed on a tree limb. Views of the skull are also provided by Jentink. Number and position of teats match the pattern seen in all members of the P. leucomus group (one postaxillary pair, two inguinal pairs). Conformation of the skull is closely similar to that illustrated for P. alstoni and P. topapuensis (figs. 12–Fig. 1314); cranial and dental measurements are summarized in table 17. See the account of P. alstoni for additional information.

Comparisons

Prosciurillus weberi is allopatric to the geographic ranges of P. alstoni and P. topapuensis and requires close comparisons with those species. Contrasts are described in those two accounts.

Geographic Variation

Because the few specimens of P. weberi are from the same small geographic area, we cannot assess the nature of geographic variation in this species.

Ecology

Other than knowing that the collection localities were in lowland tropical evergreen rain forest, we have no other information about the biology of P. weberi. We suspect that its habits are similar to those of P. topapuensis and P. alstoni, which inhabit the upper canopy and eat mostly soft fruits, seeds, and insects.

Ectoparasites

No records.

Sympatry

Only Rubrisciurus rubriventer has been collected at the same place as P. weberi (see gazetteer and table 6), but P. murinus probably inhabited the same forests at the time the specimens of R. rubriventer and P. weberi were collected.

Synonyms

None.

Prosciurillus topapuensis (Roux, 1910)

Sciurus topapuensis Roux, 1910: 518.

Callosciurus leucomus hirsutus Hayman, 1945: 576.

Holotype and Type Locality

The holotype of Prosciurillus topapuensis is an adult female (NMB 1628/4245) collected by Paul and Fritz Sarasin on September 16, 1902. A dry skin and accompanying skull comprise the holotype. The skin is an intact flat pelt. Most of the skull is present; the right zygomatic arch, most of the basioccipital and the occipital condyles are missing, as are the left third and fourth premolars and third molar. The mandible is complete except for missing coronoid processes, and all teeth are missing from the right dentary. Measurements are listed in table 13.

The type locality is Gunung Topapu (approximately 02°S, 120°15′E; estimated from a copy of the original map used by Paul and Fritz Sarasin), 1550 m (locality 16 in gazetteer and map in figure 11). This highland is contained in the mountains west of Teleboi in the Bada region of the west-central region of Sulawesi, the north and western portion of Propinsi Sulawesi Selatan, Indonesia.

Our identification of the holotype of topapuensis as an example of the P. leucomus group requires explanation. A single specimen is the basis of Roux's (1910: 518) description of Sciurus topapuensis and his account is short (translated from the original in German; the German text is reproduced in appendix 5):

Roux compared the skin with “Sciurus tonkeanus” [ =  Prosciurillus alstoni], noting close resemblance between the two in color of the fur over the head, back, and tail, but a sharp difference in coloration of the underparts. Instead of being “brick red” as in tonkeanus, the venter was described as grayish yellow, the base of the hairs being gray and the tips yellow. Later in the account, Roux referred to the underparts as gray. He also noted the presence of distinct ear tufts the same color as the head, and that the yellowish tone seen on the back was brighter along sides of the body and on the limbs.

Roux's references to “yellow” (“gelb”) and “yellowish” (“gelblich”) actually refer to slightly different buffy tones. On all specimens we assign to P. topapuensis (see gazetteer), the dorsal fur is a rich brown with buff highlights intermixed with black, a reflection of the black and orange or buff banding on the overhairs. Sides of the body and dorsal surfaces of the limbs are slightly paler (grayer) because the buffy bands of the hairs are much paler than those on the back, ranging from pale buff to cream. The coat covering underparts of these specimens is dark gray speckled or washed with pale buff or cream—the hairs are gray for most of their lengths and tipped with pale buff or cream, a combination reflecting Roux's “yellowish buff.” Overall, the underparts appear dark gray flecked with buff, as Roux noted (a few specimens have dark gray underparts tinted with silver—a dark grayish white), and contrast sharply with the reddish venters common to all the other species in the P. leucomus group. Most specimens we examined exhibit black ear tufts ranging in expression from prominent to less conspicuous; a few individuals sprout tufts containing fewer black hairs with the result that the ears appear nearly inseparable from color of the head, the pattern Roux described for the single specimen of topapuensis he examined.

Coloration of the fur on the skin of the holotype of topapuensis has altered through the years in storage. Loïc Costeur kindly sent us a color image of the skin, which is preserved flat, unstuffed. The black bands on hairs of the back are now dark brown, the buffy bands yellow (the color of straw); the remnants of the underparts are paler than upperparts but yellowish with only a hint of the original gray.

Although the skull of the holotype is damaged, Loïc Costeur was able to measure all but four of the cranial and dental dimensions we investigated (table 26) and the values were included in our multivariate analyses. In the ordination showing specimen scores projected onto first and second principal components in figure 26, the score representing the holotype of topapuensis clusters with those for specimens from Sungai Miu and Sungai Sadaunta; falling nearby are the scores representing specimens from Gunung Kanino, Besoa, and Rano Rano.

Emended Diagnosis

Prosciurillus topapuensis shares with other members of the P. leucomus group a body moderate in size (tables 15, 16), but contrasts with the other four species by the following combination of pelage traits (see table 12): (1) tail averages shorter relative to length of head and body; (2) dorsomedial surface of each ear covered with long black hairs projecting beyond ear rim to form a conspicuous black tuft on most specimens; (3) no bright ochraceous hairs lining inside of the pinnae, which is the same color as the fur on neck and head; (4) no nape patches behind the ears; (5) no middorsal black stripe extending along the back from neck to base of tail (6) fur over upperparts thicker and subdued in tone on squirrels from high altitudes; (7) dark gray underparts lightly brushed with silver, pale buff, or ochraceous tones; and (8) a geographic range restricted to the western mountainous portion of Sulawesi's central core, where the species ranges in altitude from tropical lowland evergreen rain forests covering foothills to montane rain-forest formations.

Geographic and Altitudinal Distributions

Voucher specimens identified as P. topapuensis describe a range concordant with valleys, foothills and mountains covering the western portion of the central core of Sulawesi, from Danau Lindu and surrounding highlands in the north (about 01°19′S, 120°00′E) to Pegunungan Latimojong (03°30′S, 121°23′E) in the south—the west-central region (or western mountain block) of Sulawesi's central core—and an altitudinal range from 350 m in tropical lowland evergreen rain forest to 2800 m in upper montane forest habitats (see gazetteer for P. topapuensis and map in fig. 11). Although collection sites are spotty throughout this extensive region, P. topapuensis likely occurs everywhere in suitable forested habitats. Whether it inhabits forests along the western coastal lowlands (between about 1° and 3°30′S) is unknown, for no specimens of squirrels have been collected there. This region has never enjoyed surveys documenting the diversity of small mammal species. If P. topapuensis does descend to altitudes along the coastal plain just above sea level, it would be in forests covering these western lowlands bordering the Makassar Strait. On the other hand, possibly a different member of the P. leucomus groups inhabits those coastal forests. A good candidate is P. weberi, which is currently known from only two places east of the mountains in the lowlands fringing Teluk Bone. Conceivably, the species could be found in the lowlands flanking the southern margins of the central mountains and all along the western coast in lowland forests fringing the western flanks of the mountainous central region.

We cannot, however, dismiss a speculation that P. topapuensis may inhabit only foothills and mountains but not along the coast. Along Musser's transect in the northern portion of Sulawesi's southern core, he collected different species of squirrels from 290 m to the summit of Gunung Nokilalaki above 2200 m. The lowest elevation was along Sungai Oha Kecil, a tributary of the Sungai Miu and downriver from the camp at 350 m, which is the lowest record for P. topapuensis. Musser trapped along the Oha Kecil and in the adjacent hillsides employing long traplines that included many Conibear traps. He caught only the large-bodied Rubrisciurus rubriventer and the much smaller-bodied Prosciurillus murinus (see those respective gazetteers). No examples of P. topapuensis were encountered or even seen in the forest until the Sungai Miu camp and higher along the Sungai Sadaunta. We need more inventories of tree squirrels derived from transects extending into coastal lowlands elsewhere along the western coastal flanks of the west-central mountain block.

No specimens of squirrels in the P. leucomus group are available from the highlands between the Danau Lindu region and approximately 80 km to the north in the basal portion of the northern peninsula at Bumbarujabu (00°43′S, 120°04′E). The sample from Bumbarujabu is P. leucomus, exhibiting a very different pelage pattern and found only on the northern peninsula (see section on comparisons). We do not know where the geographic range of P. topapuensis ends in this unsurveyed interval and that of P. leucomus begins.

The forested lowlands east of the mountainous range of P. topapuensis, from south of Parigi along the fringing eastern coast to the eastern portion of the central core, are inhabited by populations of P. alstoni, another member of the P. leucomus group characterized by a color pattern strikingly different than seen in P. topapuensis (see comparisons). In the Mapane region at the southern margin of Teluk Tomini, the distance between collection sites for P. alstoni at Mapane and Pinedapa and to the west in the mountains at Rano Rano where P. topapuensis was encountered is only about 20 airline km. Other collection sites for each species are much farther apart—where the western range boundary for P. alstoni lies relative to the eastern boundary for P. topapuensis is not known (see the account of P. alstoni for details). The eastern flanks of the mountainous central core—generally west of a line extending from the Mapane region in the north through the west side of Danau Poso to the western foothills in the south in the areas west of Masamba, Palopo, and the eastern flanks of Pegunungan Latimojong may delimit the eastern range boundary for P. topapuensis, at least where suitable forest habitats persist and in the past when forest cover was less altered than at present.

In the Masamba and Palopo lowlands west of the central mountains, the indigenous member of the P. leucomus group is P. weberi, not P. alstoni (see that account). In this area the mountainous range of P. topapuensis sits adjacent to that of lowland P. weberi, which has been collected only around Masamba (02°34′S, 120°19′E) and Palopo (03°01′S, 120°13′E).

The southern flanks of Pegunungan Latimojong and the adjacent highlands to the west likely mark the southern boundary of the range of P. topapuensis. This end of the west-central mountainous core of Sulawesi is separated from the southern portion of the southwestern peninsula by the Tempe Depression, a lowland trough containing flood lakes over which a river may have flowed in the past. One of the lakes, Danau Tempe, “… appears to be a remnant of an ancient strait that formerly separated the southern arm of the Toraja highlands [Pegunungan Latimojong and highlands to the north] from southern Sulawesi” (Whitten et al., 1987: 259). No modern specimens of the P. leucomus group have been collected south of the Tempe Depression, but a member once occurred there and that population is represented by a subfossil fragment (see account of Prosciurillus sp.).

Available voucher specimens of Prosciurillus topapuensis identify it as part of the mammalian fauna endemic to the west-central region in Sulawesi's central core. This is the area of foothills, interior valleys, and mountain peaks lying west of Danau Poso, and extending from the Palu area in the north to Pegunungan Latimojong in the south. In addition to P. topapuensis, samples of three species of shrews (Crocidura), one or two primates (Tarsius), a ground squirrel (Hyosciurus), and 13 species of murid rodents have been collected so far only from the west-central foothills, valleys, and mountains (table 25).

TABLE 25

Mammal Species Currently Recorded Only from the West-Central Region in Sulawesi's Central Core^a

Description

Prosciurillus topapuensis has dark brown upperparts, black ear tufts, and dark gray underparts washed with buff or silver. The squirrel is similar to P. leucomus and P. alstoni in body size and most physical proportions (length of head and body, 151–190 mm; length of hind foot, 40–49 mm; length of ear, 15–21 mm; weight, 130–210 g; see tables 15, 16). Thickness and color of the fur covering upperparts of head and body are also similar; all three species possess a uniformly thick coat (12–15 mm) that is dark brown flecked with black and orange along midline of the body from forehead to base of tail, but grading into a slightly paler brown spotted with black and pale buff along sides of the head, body, fore-legs, and hind legs. Dorsal surfaces of the front and hind feet may be the same color as the head and back, slightly darker, or slighter paler (buffy gray). Coloration of the body fur results from the mixture of dark gray curly underfur; longer overfur composed of hairs each of which is blackish gray with a subterminal orange or buffy band and black tip; and black guard hairs barely projecting beyond the overhair layer (about 5 mm). Animals from high altitudes in montane forests tend to be slightly paler; the subterminal bands on the overhairs are buff instead of orange, and the dorsal coat slightly thicker.

The dorsal background forming upperparts of P. topapuensis is interrupted by a buffy ring encircling each eye, a buffy muzzle and chin, and black ear tufts. Glossy black hairs cover the medial surface of each pinna and extend beyond its margin to form a short (4–8 mm) black tuft, closely similar in configuration to the tufts in the samples of P. leucomus from the northern peninsula. Within the sample, the tufts vary in their expression, and are so reduced in one specimen (a few black hairs) as to be inconspicuous—this squirrel has a uniform dark brown back with buff and black highlights. Prosciurillus topapuensis lacks any sign of nape patches behind the ears—fur covering top and sides of the neck is indistinguishable in color from the rest of the upperparts—or a black middorsal stripe.

Fur covering the underparts from chin to base of the tail is moderately thick (up to 10 mm) and very dark gray with silver highlights (dark grayish white) or washed with pale buffy or ochraceous hues. The overhairs are dark gray for two-thirds of their lengths and unpigmented at the tips or retain pale buffy or ochraceous bands. Dark grayish white venters are infrequent in our sample of P. topapuensis, and even those specimens with primarily silver-tinted venters exhibit small buffy infusions on the chest. The ventral coloration hardly contrasts with that of the upperparts.

The tail of P. topapuensis is shorter than the length of the head and body (LT/LHB  =  84%–96%, see table 16) and is covered in long hairs, each patterned by alternating black and buffy or orange bands. The overall effect is rings of black and buff with buffy and short black bands outlining margins of the tail and long black hairs forming a black terminal tuft. The ventral surface of the tail resembles the upperparts, dark brown with orange and black highlights bordered by black and buffy margins. Overall coloration of the tail is similar to that seen in P. leucomus, P. alstoni, and P. weberi, but somewhat browner.

As with the other members of the P. leucomus group, female P. topapuensis have three pairs of teats, one abdominal pair and two inguinal pairs. One female with enlarged teats exhibited a placental scar in the right uterine horn; other females examined, although adult, showed no reproductive activity.

Views of the skull are provided in figures 12–Fig. 1314; cranial and dental measurements are summarized in tables 17 and 26.

TABLE 26

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Population Samples of Prosciurillus topapuensis Mean ± 1 SD and observed range (in parentheses) are listed.

Comparisons

Prosciurillus topapuensis requires comparisons with P. leucomus, which ranges to the north throughout the northern peninsula, and P. alstoni and P. weberi, both occurring in lowlands adjacent to the mountainous distribution of P. topapuensis. See the account of P. alstoni for contrasts between it and P. topapuensis; here we describe differences between P. topapuensis and the other two species.

Prosciurillus topapuensis and P. leucomus: Body size is comparable in the two species, but the tail averages shorter relative to length of head and body in P. topapuensis (tables 15, 16). Representatives of P. topapuensis from lower altitudes show a dorsal coat similar in thickness and coloration to that of P. leucomus, but individuals from upper montane forests have a thicker, slightly duller coat, the orange and bright buffy bands of the hairs giving the lowland squirrels their speckling against the brown background are slightly paler in the montane animals. Both species have black ear tufts, but those of P. topapuensis vary in size among the samples, ranging from being prominent (like those in samples of P. leucomus) to showing only traces of black on the ears of a very few individuals; every specimen of P. leucomus has prominent black tufts. The inner surface of each ear at the base of the tuft is the same color as the rest of the head and not bright ochraceous as seen in P. leucomus. Fur behind the ears on the neck of P. topapuensis is the same color as the head and back, which is strikingly unlike that region in most specimens of P. leucomus where the neck is marked by conspicuous whitish nape patches. Finally, all examples we studied of P. topapuensis show a dark gray coat highlighted with silver or hues of buff and ochraceous covering the underparts; the ventral fur of P. leucomus ranges from reddish orange to ochraceous (table 12). Specimens of P. topapuensis appear monochromatic (brownish gray everywhere), those of P. leucomus are bicolor (dark brown upperparts, reddish underparts).

As with all members of the P. leucomus group, skulls of P. topapuensis and P. leucomus closely resemble one another in general size and shape but contrast in average size and proportions of some dimensions. Except for length of nasals, breadth of rostrum, and height of braincase, cranial and dental dimensions average less in the sample of P. topapuensis compared with P. leucomus (table 17). That difference can also be visualized by results of multivariate analyses illustrated in an ordination showing specimen scores projected onto the first and second principal components extracted from principal-components analysis (fig. 24). The group of scores representing geographic samples of P. leucomus overlaps with the cloud of points identifying specimens of P. topapuensis along the first component (an estimate of size) but is pushed slightly farther to the right by the moderate to high positive loadings of all variables except height of braincase (table 27). Fewer variables strongly influence the distribution of scores along the second axis, which reflects shape distinctions. Compared with P. topapuensis, the northern peninsular species P. leucomus has a relatively wider interorbit, mastoid region, and bony palate, and longer orbit and auditory bulla, but relatively shorter nasals, diastema, and tooth row, and narrower rostrum. These are subtle shape differences but some of them, especially the narrower interorbit and shorter orbit of P. topapuensis, are visually apparent when skulls of each species are compared side-by-side.

Fig. 27

Habitat of Prosciurillus topapuensis in lower montane rain forest on Gunung Kanino, 1440 m. The large, darker tree in the center of the photograph is the oak Lithocarpus glutinosus. Prosciurillus murinus and Rubrisciurus rubriventer occupy this forest as does the ground squirrel Hyosciurus ileile. This elevation is close to the upper altitudinal limits of R. rubriventer and H. ileile. See table 2 for the range of ambient temperatures recorded during the sampling period. Photographed in 1975.

TABLE 27

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus topapuensis with Those of Prosciurillus leucomus Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 24.

Prosciurillus topapuensis and P. weberi: These two species are similar in body size and contrast in relative tail length along with fur texture in much the same way as seen between P. topapuensis and P. leucomus. The former has a shorter tail relative to length of head and body, duller upperparts, and dark grayish buff or grayish white underparts instead of the reddish orange covering typical of P. weberi. Both species lack nape patches, both exhibit black ear tufts, but the back of P. topapuensis is unmarked by a black middorsal stripe, which is so conspicuous on all examples of P. weberi.

The ordination of specimen scores projected onto the first and second principal components extracted from principal-components analysis in figure 25 summarizes our multivariate analysis of the cranial and dental variables we employed. No separation of the scores representing specimens of each species is apparent along the first axis, a general estimate of size, partly because the sample of P. weberi is so small compared with that of P. topapuensis, and partly because of the breadth of individual and geographic variation in that species as indicated by the wide scatter of points along the first component, which is influenced by the moderate to high positive loadings of most variables (table 28). The few variables primarily contributing to the spread of scores that form two nearly separate constellations along the second axis reflect contrasts in shape. Prosciurillus weberi has a relatively broader rostrum compared with P. topapuensis and relatively shorter nasals and tooth rows. This analysis needs to be revisited employing a much larger sample of P. weberi than is currently available.

Fig. 28

Collection localities for samples of Prosciurillus rosenbergii in the Sangihe Archipelago (Kepulauan Sangihe) north of mainland Sulawesi's northeastern tip. Samples come from Pulau Sangihe, Pulau Siau, and Pulau Tahulandang and the nearby Pulau Ruang. Prosciurillus rosenbergii is the only squirrel ever collected in this group of islands and occurs nowhere else. To the south, off the northeastern tip of Sulawesi's northern peninsula, P. murinus, which is found throughout the mainland, has been collected on Pulau Talisei and Pulau Lembeh, and P. leucomus, ranging over the northern peninsula, is recorded from P. Lembeh (see gazetteers for these two species).

TABLE 28

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus topapuensis with the Sample of Prosciurillus weberi Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 25.

Geographic Variation

Every example of P. topapuensis from the west-central mountain block is immediately recognizable by its short and black ear tufts, unpatterned neck and back, and very dark grayish white or grayish buff underparts. Variation in color patterning over the fur covering head and body appears to be altitudinal and individual rather than regional. Examples from high altitudes, usually in upper montane forests, have slightly thicker and duller upperparts than those taken in the foothills and lower places. Extent of the ear tufts range from being conspicuous on most squirrels to nearly hidden in the fur surrounding the ears in a very few specimens, and underparts range from dark gray speckled or washed with buff or ochraceous to dark gray lightly sprinkled with white (appearing as silvery highlights); these expressions in ear tufts and tone of underparts occur within the same sample as well as among population samples and do not appear to be correlated with altitude.

Body size may vary with altitude. Along Musser's transect, the only line along which samples have been collected that extends from tropical evergreen rain forests in the lowlands to montane rain-forest habitats in adjacent highlands, squirrels from Sungai Miu and Sungai Sadaunta, in lowland evergreen rain forest between 350 and 915 m, average slightly greater in many body and cranial dimensions than do those collected from higher altitudes along the transect, and from mountains east and south of the region where Musser worked (tables 16, 26).

Results of multivariate analyses of cranial and dental variables as presented in the ordination of specimen scores projected onto the first and second principal components extracted from principal-components analysis in figure 26A reflect the altitudinal variation in size and also identifies a regional component. Covariation in nearly all variables contributes to the spread of scores along the first axis (table 29), reflecting increasing size from left to right, with points for most geographic montane samples intermingled, and scores representing samples from Sungai Miu and Sungai Sadaunta (350–915 m) anchoring the right sector of the constellation. Scores representing squirrels collected between 1400 and 1500 m on nearby Gunung Kanino are sprinkled through the cloud from the right to the center.

Fig. 29

Subfossil fragment from a right dentary of Prosciurillus sp. (AMNH 269955) from Ulu Leang I, a cave about 40 km northeast of Ujung Pandang in the Maros region near the tip of Sulawesi's southwestern peninsula. Size of the fragment fits with dentaries typical of species in the Prosciurillus leucomus group, which in this figure is represented by P. alstoni (bottom labial and lingual views, AMNH 101331) from Wawo in the southeastern peninsula (see gazetteer and fig. 11 for Prosciurillus sp. and P. alstoni), and not the smaller-bodied P. murinus (top set, AMNH 101388), represented here by a sample from Lombasang on the flank of Gunung Lompobatang, east of the Maros region on the southwestern peninsula (see gazetteer and map in fig. 30 for P. murinus). All views are ×2. Additional information is presented in the text and table 33.

TABLE 29

Results of Principal-Components Analysis of Population Samples of Prosciurillus topapuensis All variables are employed, but the holotypes of topapuensis and hirsutus are excluded because the skulls are damaged. Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 26A.

TABLE 30

Results of Principal-Components Analysis of Population Samples of Prosciurillus topapuensis Fewer variables are used than listed in table 29 to accommodate the damaged holotypes of topapuensis and hirsutus. Principal components are extracted from a covariance matrix of log-transformed values for 10 cranial and 1 dental variable; see figure 26B.

Scores for specimens from Gunung Lehio (crosses in fig. 26A), just south and east of Musser's transect, are scattered in the constellation from left to right along the first component and also tend to lay along the outskirts of the larger cluster from the perspective of the second axis. This alignment suggests the sample from Gunung Lehio to have a relatively wider rostrum and bony palate, longer tooth row, and shorter diastema as compared to specimens in the other geographic samples (table 29).

We can easily describe the results diagrammed in the principal-components ordination but assessing the significance of the pattern is difficult without additional samples. Certainly variation in size of skull concomitant with age reflects one component of the broad spread of scores along the first axis—samples are mixed, containing the range from young adults to old adults. Comparing larger samples, each composed of the same relative age, may better resolve the true pattern of altitudinal and regional variation. Musser's small samples from low altitudes are highlighted in the cluster of scores, suggesting that populations in lowlands and foothills may average larger in body size than those living at higher altitudes in montane forest habitats. This aspect of variation gleaned from study of material at hand needs to be tested by larger samples collected along transects from different regions in the mountainous western section of Sulawesi's central core. Finally, some populations of P. topapuensis may be partially isolated from one another by large rivers or other kinds of geographic barriers, which might be revealed by a greater density of sampling over the geographic range that we have described.

We were tantalized by the average differences in body size between the two samples of squirrels, one from 350–915 m and the other from higher altitudes, because among other groups of mammals, especially murid rodents, there is a pattern of closely related species replacing each other with altitude generally concordant with forest type in the western mountain block of Sulawesi's central core (table 31). One set of shrews (Crocidura), bats (Thoopterus), tarsiers (Tarsius), and squirrels (Hyosciurus), and three sets of murid rodents (Bunomys, Haeromys, and Margaretamys) collected along Musser's transect, from the lowlands in the Sungai Miu region to the summit of Gunung Nokilalaki in montane forests provide examples. The lowland species in each of these sets is very distinctive compared with their respective montane relatives; the dissimilarity is expressed in body size, fur coloration, and marked contrasts in cranial conformations along with cranial and dental dimensions.

TABLE 31

Tropical Lowland Evergreen Rainforest Species, Their Montane Forest Replacements, and the Species Found in Both Lowland and Montane Forests in the West-Central Region of Sulawesi's Central Core^a

No such marked morphological differences contrast squirrels in the samples of P. topapuensis from Sungai Miu and Sungai Sadaunta compared with those collected on the slopes of Gunung Kanino or even higher in other parts of the western mountain block. Specimens in each set of samples are indistinguishable in fur coloration and expression of black ear tufts, those from the lower altitudes simply average slightly larger in body size and have slightly brighter upperparts. Apparently the same species ranges from foothills to higher in the mountains, which parallels the altitudinal distributions of two species of Crocidura, one macaque, two other tree squirrels, and six species of murid rodents (table 31).

Ecology

Prosciurillus topapuensis inhabits the upper canopy of primary forest. In all the different altitudinal forest formations, the squirrels mostly remain in crowns and woody vines forming the upper canopy. They are active in the mornings and afternoons during sunny days, but might be active all day long on cloudy days. They travel through the upper canopy, but come to the ground occasionally, especially in places where the canopy is broken. When on the ground, the squirrels run on trunks and limbs lying on the forest floor and regularly cross streams and rivers along bridges formed by branches of live trees arching over the water as well as rotting tree trunks and limbs and palm trunks connecting opposite stream terraces. Most of Musser's specimens were trapped on these kinds of river and stream crossings (habitats at trap sites are summarized in table 32).

TABLE 32

Summary of Habitat at Trapping Sites, Stomach Contents, and Other Relevant Information for Specimens of Prosciurillus topapuensis Collected by Musser in Central Sulawesi, 1973–1976 Collection locality, specimen number, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). Three of the collection localities (Sungai Miu, Sungai Sadaunta, and Tomado) are in tropical lowland evergreen rain forest; lower montane rain forest describes the places on Gunung Kanino, and tropical upper montane rain forest the site on Gunung Nokilalaki. With one exception, all squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

Musser encountered P. topapuensis all along the transect line, from Sungai Miu at 350 m to the summit of Gunung Nokilalaki at 2300 m (see photograph of forest on Gunung Kanino in fig. 27), from lowland evergreen rain forest to upper montane rain forest, and through a range of ambient temperatures (table 2) and habitats—forested stream terraces, hillsides, and ridgetops. Although wary and quiet in the forests around Tomado at 1000 m, and usually seen only in tree crowns forming the high canopy, the squirrels were aggressive and loud elsewhere along the transect line. At higher altitudes along the Sungai Tokararu and slopes of Gunung Kanino (1150–1500 m), for example, P. topapuensis was common, aggressively vocal, and unwary—Musser saw squirrels there every day. On several different days he would be walking along the trapline and every time he stopped to rebait a trap a squirrel would begin its loud, resonant, scolding chatter, always positioned just out of reach above his head. The squirrel remained quiet as long as Musser kept walking, but once he stopped the scolding began again until he left the area. On one occasion, a squirrel was in the crown of an understory tree isolated from nearby trees. To get out of the tree, the squirrel had to come to the ground but would not do so while Musser was there. It would scamper out to the end of a branch, stop and stare at Musser, then run to a different branch, all the time its tail twitching spastically with each raspy chuck. On another day, a squirrel left the upper canopy descending to the trunk where it stopped, splayed against the bark, head down, and tail flipping in agitated undulations with each loud chatter. It scolded for one or two minutes, then would run back up into the crown and disappear from sight. In addition to human presence, the squirrels were very sensitive to human voices, the sounds of trees falling in the forest, or even a limb hitting the ground, and the sights of hawks and eagles—all elicited a cacophony of strident loud chatter.

Fig. 30

Collection localities for samples of Prosciurillus murinus and P. abstrusus. Numbers key to localities described in the gazetteer where specimens are identified by museum initials and catalog numbers. The inset map, right (rectangle in larger map, above), contains collection localities (17–36) for P. murinus, which are scattered along Musser's transect from the Sungai Oha Kecil to the higher ramparts of Gunung Nokilalaki. The dashed contour line at 1300 m marks the approximate boundary between tropical lowland evergreen rain forest and tropical lower montane forest.

The sound of rain approaching in the forest also prompted alarm calls from squirrels and some birds. After the clouds build up and the sky darkens, and just before the torrent begins there is a period of absolute silence in the forest, shattered only by birdsong and a squirrel's resonant chucks. The squirrels call individually, not in chorus, and cease as the first drops splatter against the leaves, signaling the more intense approaching rain, which passes through the forest like a moving wet curtain. Several times Musser saw a squirrel on a large woody vine in the upper canopy calling in a long series of chattering chucks, then dart into a hole in the nearest tree just before the first drops were felt.

Musser looked for leaf nests but never found them. At one camp he passed a tall strangler fig on the way to check traps. The host tree had long since decayed and the enclosing trunk was filled with debris and leaf litter, held tightly by the criss-cross patterns of ropy trunk. Each day he would see a pair of squirrels in the crown, running over the upper trunk, limbs, and along the huge woody vines encircling the trunk. Periodically they would disappear into a space between the latticework, and then reemerge. One evening he watched them chase each other, feed on figs, and eventually disappear out of sight inside the trunk. Tall strangler figs are common in lowland rain forest and offer numerous sites for nests within the debris-filled hollows. Likely, cavities in other kinds of trees are also used for nest sites by P. topapuensis.

Judged by contents of stomachs, the diet of P. topapuensis consists of soft fruits, especially figs, some seeds, and arboreal insects (table 32). All the different fruits were thoroughly masticated, and only figs could be positively identified (pieces of rind and endosperm with tiny seeds attached). The insects consisted of small adult beetles (represented by fragments of wings, elytra, legs, and sclerites), macrolepidopteran caterpillars (whole or chewed into pieces) gleaned from surfaces of leaves and bark, and cockroaches (indicated by legs, antennal segments, wings, and masticated bodies). Beetles were uncommon in stomachs, but the caterpillars must be a favorite prey. Remains were found in many stomachs, and of these one (AMNH 225501) was distended with large (20–30 mm long) macrolepidopteran caterpillars, many of them still in one piece. The stomach of another squirrel (AMNH 225504) was packed with smaller (10–15 mm long) macrolepidopteran larvae, whole and in pieces. Both squirrels were caught on Gunung Kanino above 1400 m (table 32). Cockroaches are in the trees and on the ground. Soft fruits and insects also comprise the diet of the genetic and geographic relative P. alstoni, but the range of insect groups encountered in stomachs of that species was greater than that recovered from stomachs of P. topapuensis (table 24).

Ectoparasites

Prosciurillus topapuensis is parasitized by a host-specific sucking louse, Hoplopleura topapuensis, n. sp. (described in a following section), as well as two species of flea (table 56). Sigmactenus sulawesiensis (Siphonaptera, Leptopsyllidae) is recorded from a voucher host collected at Tomado, and the same species of flea also parasitizes five species of endemic Sulawesian murid rodents: Bunomys fratrorum, B. penitus, Eropeplus canus, Maxomys musschenbroekii, and Paruromys dominator (Durden and Beaucournu, 2000). Murids are typical hosts of Sigmactenus spp. fleas (Durden and Traub, 1990) so the record of S. sulawesiensis from P. topapuensis is likely an atypical host association (Durden and Beaucournu, 2000). Farhangia sedecimdentata (Pygiopsyllidae) was found on voucher squirrels collected at Sungai Tokararu and Gunung Kanino, and to date has not been discovered parasitizing other rodents (Mardon and Durden, 2003). The squirrel hosts were initially identified as Prosciurillus leucomus. Farhangia spp. are considered to be “nest fleas” of Asian (Bornean and Sulawesian) tree squirrels (Traub, 1980); F. sedecimdentata is therefore probably more common in nests of P. topapuensis.

Sympatry

The range of P. topapuensis in the central core of mainland Sulawesi overlaps those of the tree squirrels P. murinus, Rubrisciurus rubriventer, and both species of ground squirrels, Hyosciurus (table 6). Along his transect in the northern portion of central Sulawesi, Musser caught P. topapuensis in the same traplines along with examples of those four species, and sometimes in the same traps (see table 32).

Synonyms

Only one scientific name is a synonym of P. topapuensis: reasons behind its allocation are presented below.

Callosciurus leucomus hirsutus Hayman 1945: 576. HOLOTYPE: BMNH 40.691g (stuffed museum study skin and slightly damaged skull; see table 13 for measurements), an adult male collected by W.J.C. Frost in 1938 or 1939. TYPE LOCALITY: Tamalanti, a “Plantation between Rantekaroa [02°50′S, 119°50′E] and Koelawi [01°27′S, 119°59′E]” (Laurie and Hill, 1954: 156), 3300 ft (1006 m), in the western portion of the central core of the island, Propinsi Sulawesi Selatan, Indonesia.

Frost collected six tree squirrels from Tamalanti, and Hayman (1945: 577) considered them to represent a member of the “peculiar leucomus group” and diagnosed Callosciurus leucomus hirsutus this way:

“The shaggy coat is particularly long and full in [hirsutus]” wrote Hayman (1945: 578), “and in conjunction with the tufted ears and particularly long terminal tail tuft suggested the subspecific name.” While Hayman appreciated the unique coloration of the fur characterizing hirsutus, he did not consider it to be diagnostic of a separate species; “Callosciurus leucomus hirsutus is strikingly different from C. leucomus leucomus of N. E. Celebes in colour, but is here treated as a subspecies to indicate relationship, in view of its obvious affinities as shown by the skull” (Hayman, 1945: 578). Hayman acknowledged that among the named forms of Callosciurus leucomus (mentioning leucomus and occidentalis but not alstoni, tonkeanus, sarasinorum, mowewensis, or elbertae), hirsutus resembled only Roux's (1910) Callosciurus topapuensis, which he knew only from Roux's published description, writing “But topapuensis is said to have ear tufts coloured as the head, and to have the sides of the body, and the limbs a lighter, more yellowish, tone than the back, two characters which definitely do not apply to the Tamalanti form.” But these tonal aspects of Roux's description do apply to all six of Hayman's hirsutus. In these and all examples of the other species in the Prosciurillus leucomus group, sides of the body and dorsal surfaces of the limbs and feet are slightly paler than the back due to the pale buff or cream bands on the overhairs in the fur covering these regions, as we explained above. The contrast in color of the ear tufts, from concolorous with the head, as in the holotype of topapuensis, to black as described by Hayman for hirsutus reflects extremes in the range of variation we see within our sample from several highland regions in the central core of Sulawesi.

Some dimensions of the skull from the holotype of hirsutus (kindly measured for us by Paula Jenkins) are slightly smaller than those for the holotype of topapuensis (table 13). This distinction is reflected in the ordination of specimen scores projected onto first and second principal components derived from principal-components analysis that is shown in figure 26B where the score for hirsutus falls among scores representing specimens from Rano Rano, Gunung Lehio, Besoa, and Pegunungan Latimojong. Mean values for cranial dimensions average smaller in these highland samples than in the material from Sungai Miu and Sungai Sadaunta, which is closer to the holotype of topapuensis in size of skull. Again, the two holotypes represent variation within a single species, this time in cranial dimensions, with the skull of hirsutus nesting with the smaller specimens and that of topapuensis with the larger individuals (fig. 26B, table 30).

Prosciurillus rosenbergii (Jentink, 1879)

Sciurus Rosenbergii Jentink, 1879: 37.

Sciurus tingahi Meyer, 1896: 27.

Lectotype and Type Locality

The lectotype of Prosciurillus rosenbergii is a young adult female (RMNH 13362, specimen “l” in Jentink's [1888: 24] catalog) obtained by D. Hoedt on October 27, 1865, from “Siao,” Kepulauan Sangihe. It consists of a skin mounted in a live pose and an incomplete skull (extracted from the mount after Jentink's tenure at Leiden). Values from dental and some cranial measurements are listed in table 14.

Specimen “l” was one of 12 specimens cataloged as “types” ( =  syntypes) by Jentink (1887: 190–191, 1888: 23–24). All the skulls are badly damaged or smashed. At the suggestion of Chris Smeenk (in litt., 2008), we select specimen “l” as lectotype following the procedure stipulated in Article 74.1 of the Code; ICZN, 1999: 82). Of the 12 syntypes, specimen “l” “has a beautiful skin and the second best skull” (C. Smeenk, in litt., 2008). The remaining 11 specimens become paralectotypes: (1) specimen “a” (Jentink,1888: 23), RMNH 13351, a mounted skin and incomplete skull, male, from “Sanghi” ( =  Pulau Sangihe or Kepulauan Sangihe), collected November 7, 1864, by collectors for C.B.H. von Rosenberg; (2) specimen “b” (Jentink, 1888: 23), RMNH 13352, a mounted skin and cranial fragments, female, from “Sanghi” ( =  Pulau Sangihe or Kepulauan Sangihe), collected November 2, 1864, by collectors for C.B.H. von Rosenberg; (3) specimen “c” (Jentink, 1888: 23), RMNH 13353, a mounted skin and incomplete skull, female, from “Sanghi” ( =  Pulau Sangihe or Kepulauan Sangihe), collected November 10, 1864, by collectors for C.B.H. von Rosenberg; (4) specimens “a” (the skull, in Jentink's osteological catalog, 1887: 190) and “d” (the skin, in Jentink, 1888: 24), RMNH 13354, a mounted skin and incomplete skull, male, from “Sanghi” ( =  Pulau Sangihe) collected January 16, 1866, by D. Hoedt; (5) specimen “e,” RMNH 13355, a mounted skin and incomplete skull, male, from “Siao” ( =  Pulau Siau) collected October 20, 1865, by D. Hoedt; (6) specimens “b” (the skull, in Jentink, 1887: 190) and “f” (the skin, in Jentink, 1888: 24), RMNH 13356, a mounted skin and incomplete skull, male, from “Siao” ( =  Pulau Siau) collected October 23, 1865 by D. Hoedt; (7); specimen “g” (Jentink, 1888: 24), RMNH 13357, a mounted skin and fragments of a skull, male, from “Siao” ( =  Pulau Siau) collected October 22, 1865 by D. Hoedt; (8) specimens “c” (the skull, in Jentink, 1887: 190) and “h” (the skin, in Jentink, 1888: 24), RMNH 13358, a mounted skin with incomplete skull, male, from “Siao” ( =  Pulau Siau) collected October 24, 1865, by D. Hoedt; (9) specimen “i” (Jentink, 1888: 24), RMNH 13359, a mounted skin along with skull fragments, male, from “Siao” ( =  Pulau Siau) collected October 24, 1865, by D. Hoedt; (10) specimens “d” (the skull, in Jentink, 1887: 192) and “j” (the skin, in Jentink, 1888: 24), RMNH 13360, mounted skin and damaged skull, male, from “Siao” ( =  Pulau Siau) collected November 9, 1865, by D. Hoedt; (11) specimens “e” (the skull, in Jentink, 1887: 192) and “k” (the skin, in Jentink, 1888: 24), RMNH 13361, a mounted skin and partial skull, female, from “Siao” ( =  Pulau Siau) collected October 23, 1865, by D. Hoedt. Skulls “a–e,” were removed during Jentink's tenure; the others were extracted later.

The type locality is Kepulauan Sangihe, Pulau Siau (also spelled “Siao”), 02°49′N, 125°23′E (see gazetteer and map in figure 28), Propinsi Sulawesi Utara, Indonesia. No details are recorded concerning the precise collection locality on Pulau Siau.

Fig. 31

Specimen scores representing Prosciurillus murinus (filled circle; N  =  57) and P. abstrusus (filled triangle; N  =  14) projected onto the first and second principal components extracted from principal-components analysis. Arrow identifies holotype of abstrusus. See table 39 for correlations and percent variance.

Chris Smeenk (in his manuscript pages of the “Type-specimens of recent mammals in the National Museum of Natural History, Leiden”; sent to us in 2009) notes that “Jentink (1888) omitted the locality for the specimens collected by von Rosenberg. The latter did not visit the Sangir islands himself, but had sent local hunters to collect on the islands during the period September–November 1864; see his notes preserved in the archives of the Leiden Museum. It is not recorded on which island the material was collected.”

Emended Diagnosis

Prosciurillus rosenbergii is comparable in body size and length of tail relative to head and body length to other species in the P. leucomus group (tables 14, 15). It is unique among members of that cluster by having dark brown or chestnut brown upperparts without contrasting chromatic patterns (no patches on the nape behind the ears, no black middorsal stripe) or adornments (no ear tufts), dark brownish gray or brownish buff underparts (no specimen with reddish-orange to ochraceous or dark gray ventral fur) and blackish tail.

Geographic and Altitudinal Distributions

Prosciurillus rosenbergii is endemic to Kepulauan Sangihe where samples come from Pulau Sangihe, the largest island in the archipelago; the smaller Pulau Siau, south of Sangihe; and the small islands of Tahulandang and nearby Ruang (see table 4 and fig. 28). All the specimens were collected during the latter 1800s and none have information indicating elevations at which they were caught. We do not know the present status of the species in the archipelago but would not be surprised if most populations are extinct. Whitten et al. (1987: 49) write that “Virtually all of [Pulau] Sangihe has been converted to coconut and nutmeg plantations or else is covered in patches of secondary forest from abandoned gardens,” and that “Sangihe and other northern islands were largely deforested by 1920” (p. 91).

Two other species of nonvolant mammals are endemic to the Sangihe Archipelago, both recorded only from Pulau Sangihe. One is the primate, Tarsius sangirensis, which is very different in its morphology compared with samples of tarsiers from mainland Sulawesi and adjacent islands (Feiler, 1990; Groves, 2005). The other is a distinctive species of murid rodent related to those in the Rattus xanthurus group on mainland Sulawesi and nearby Pulau Peleng (Musser, ms; Musser and Carleton, 2005: 1462).

The islands forming Kepulauan Sangihe are mostly volcanos ringed by coastal lowlands scattered along the wide volcanic Sangihe arc platform, most of which is submerged about 1000 m beneath sea level (Sheets NA 51-4 and 51-12). Volcanic activity along the arc has been present since middle Miocene times (Hall, 2002: 382). Pulau Biaro, the southernmost island in the archipelago, is separated from Pulau Talise and Pulau Bangka, lying just off the Sulawesi mainland in shallow water, by sea at least 1000 m deep. There is no current evidence of any past Pleistocene or earlier land connection between the archipelago and mainland; presumably the ancestors of the few nonvolant mammals restricted to the archipelago reached the islands by some form of overwater dispersal.

Description

The highlights of Jentink's (1879: 37) description portray a squirrel characterized by coloration of fur strikingly different from any members of the P. leucomus group occurring on mainland Sulawesi and closely adjacent offshore islands.

Prosciurillus rosenbergii is comparable to squirrels in samples of P. leucomus, the member of the P. leucomus group that is closest geographicallyto P. rosenbergii, in size of body, appendages, and length of tail relative to head and body length (table 15), but strikingly different in coloration of pelage and without any of the color patterns seen in the other members of the P. leucomus complex. The entire upperparts—head, neck, back, ears, and dorsal surfaces of the feet—of specimens from the two northern islands, Sangihe and Siau, are rich chestnut-brown (Jentink's “rusty brown”), a background due to the mix of dark gray underfur, longer overhairs that are dark gray for most of their length and tipped with subterminal reddish brown and black bands, and the glossy dark guard hairs. The dorsal coat is unmarked by ear tufts, nape patches, or a middorsal black stripe. The underparts range from dark brownish gray to brownish buff and hardly contrast with color of the fur over dorsal surfaces of the head and body; hairs are dark gray basally and tipped with brown or brownish buff bands. Squirrels in samples from the southern island, Tahulandang, and its nearby smaller companion, Ruang, are slightly paler, having brown upperparts and brownish buff underparts. In all samples, the tail conspicuously contrasts with the head and body because it is blackish with rusty highlights everywhere, an effect resulting from the long black hairs with subterminal dark brown bands and long black tips (as Jentink observed, “each long hair is embellished with a broad black ring and a very long black tip.” See Feiler's (1990: 89) black and white images of P. rosenbergii and Meyer's [1896] color plate, which is reproduced in figure 9.

Females exhibit three pairs of teats, one postaxillary pair and two inguinal pairs.

Although all the skulls we examined are damaged in some way, the intact portions are closely similar to comparable cranial sections in skulls of other species in the P. leucomus group; cranial and dental measurements for some dimensions are summarized in table 17.

Comparisons

Brown or chestnut-brown upperparts, slightly paler underparts, and a blackish tail define the color pattern peculiar to P. rosenbergii. All other species in the P. leucomus group have brown upperparts flecked with orange and buff, and the underparts are reddish orange to ochraceous (P. leucomus), reddish brown to reddish orange (P. alstoni and P. weberi), or dark gray with a silver or buffy wash (P. topapuensis). The ears are the same color as the head and neck and lack tufts (conspicuous black tufts in P. leucomus, P. topapuensis, and P. weberi; white tufts in P. alstoni), no white, buffy or gray patches adorn sides of the neck behind the ears (nape patches are typical in P. leucomus) and no middorsal black stripe marks the back (diagnostic for P. weberi). The tail is blackish flecked with rust except at the tip (the tail is the same color as upperparts in the other species and only the long tuft at the end is black). Because all the skulls available for measuring are severely damaged, we cannot provide comparative morphometric analyses other than to report that mean values of those dimensions that could be measured are comparable to those derived from samples of other species in the P. leucomus group (table 17).

Geographic Variation

Other than the slight difference in color saturation of the pelage in samples from the two northern islands in the Archipelago as opposed to the southern Pulau Tahulandang and neighboring Pulau Ruang, we can provide no information on aspects of other kinds of variation that might be associated with island location. Insular variation in cranial and dental dimensions among samples from the four islands cannot be assessed because all skulls are incomplete.

Ecology

No information is available. In its morphology, P. rosenbergii is closely related to other members of the P. leucomus group, and we suspect the species to inhabit primarily the upper canopy as Musser observed for P. alstoni and P. topapuensis; only direct field observations will provide this kind of information.

Ectoparasites

No records. Durden combed the fur in a large sample of P. rosenbergii but could not locate any attached sucking lice.

Sympatry

No other species of squirrel has ever been collected on any island in Kepulauan Sangihe.

Synonyms

The only other scientific name attached to Prosciurillus rosenbergii is discussed below.

Sciurus tingahi Meyer, 1896: 27. LECTOTYPE: SNSD B2842 (stuffed museum study skin and damaged skull; see table 14 for measurements), an adult male purchased from Charles Cursham in 1894. TYPE LOCALITY: Kepulauan Sangihe, Pulau Tahulandang, 02°21′N, 125°25′E, Propinsi Sulawesi Utara, Indonesia (see gazetteer and map in figure 28). No details are recorded about the precise collection locality on Pulau Tahulandang.

Feiler (1999: 408–409) identified SNSD B2842 as the “holotype” and four other specimens as paratypes. Meyer (1896: 27) based his description of tingahi on several specimens without identifying a holotype so the specimen Feiler set aside as holotype is a lectotype and the others are paralectotypes (see Article 74.5 of the Code [ICZN, 1999: 82–83], and our accounts of P. leucomus and P. alstoni).

Although described as a separate species related to Prosciurillus rosenbergii from the northern Pulau Sangihe and Pulau Siau, we consider Meyer's sample of tingahi to represent populations of P. rosenbergii on the southern Pulau Tahulandang and closely adjacent Pulau Ruang. Specimens of tingahi have slightly paler pelage than those from Pulau Sangihe and Pulau Siau, brown upperparts and buffy brown underparts as opposed to dark chestnut brown upperparts and dark brownish gray or buff venters in squirrels from the two northern islands. Meyer's tingahi is portrayed in his color plate reproduced in figure 9.

Prosciurillus sp.

A fragment of a right dentary (fig. 29) from an adult squirrel was found in sediments excavated from Ulu Leang I, a cave about 40 km northeast of Ujung Pandang in the Maros region near the tip of Sulawesi's southwestern peninsula (see gazetteer and fig. 11). Excavations in the cave were described by Glover (1976), who also provided us with 10,000–3500 years B.P. as a rough interval of the dated sediments (Glover, in litt., 1989). A more precise date associated with the particular site (“Trench J”) at which the piece was uncovered is unavailable.

Fig. 32

Specimen scores representing seven population samples of Prosciurillus murinus projected onto the first and second principal components extracted from principal-components analysis. Symbols identifying samples are: filled circle  =  northeastern peninsula (Teteamoet, Gunung Klabat, Temboan; N  =  7); ×  =  Pulau Lembeh (N  =  4); cross  =  northern peninsula east of the Minahasa region (Sungai Paleleh, Bumbulan, Ile-Ile; N  =  9); filled upright triangle  =  Gunung Lehio (N  =  1); filled inverted triangle  =  north-central 1 (Sungai Oha Kecil, Sungai Miu, Sungai Sadaunta, Tomado, Kulawi; N  =  18); filled left-pointing triangle  =  Rano Rano (N  =  2); filled right-pointing triangle  =  north-central region 2 (Pinedapa, Kuala Navusu, Sungai Tolewonu; N  =  16). Heavy arrows identify holotypes: e, evidens; n, necopinus. Delicate arrows identify scores representing four AMNH specimens from Bumbulan, which were collected by J. J. Menden between October 10 and 25, 1939. Two others from Menden's sample, collected on October 24, 1939, are in MZB and Sody (1949: 77) had designated one of these as the holotype of “Sciurillus murinus griseus” (the holotype is currently stored in RMNH). Musser determined that the two MZB specimens were inseparable in pelage coloration and general external and cranial morphology from the AMNH series, but did not measure them. See table 40 for correlations and percent variance.

The size of the subfossil fragment (the body of the dentary) matches dimensions of the dentaries in members of the Prosciurillus leucomus group and not the two species in the much smaller-bodied P. murinus group (see fig. 29 where the subfossil is compared with a modern member of each group, and table 33 for comparative measurement values). No modern representatives of the P. leucomus group have been collected from Sulawesi's southwestern peninsula. The sample of P. weberi from Masamba and Palopo on the coastal plain in the far southeastern lowlands of the central core of Sulawesi (see map in fig. 11) is the closest to the provenance of the subfossil. At present we cannot tie the subfossil to P. weberi; or to P. alstoni, which ranges over the eastern sector of the central core of the island and throughout the southeastern peninsula; or to P. topapuensis, which inhabits forests in the foothills and mountains in the western sector of the central core north of the range of P. weberi (see map in fig. 11); or determine if the subfossil represents a different species restricted to the southwestern peninsula. Dentaries of all these species are closely similar in size and shape, especially the body of the dentary, which is all that remains of the subfossil. Possibly DNA can be extracted from the fragment and compared with samples taken from specimens of the modern species to resolve the issue.

TABLE 33

Measurements (mm) of Alveolar Lengths of Molar Rows (ALpm4–m3) in Dentaries from Samples of a Subfossil and Modern Prosciurillus^a Mean ± 1 SD and observed range (in parentheses) are listed for the extant specimens, which are identified in footnotes.

Modern specimens of the small-bodied P. murinus have been collected on the flanks of Gunung Lompobatang at the tip of the southwestern peninsula (see gazetteer and fig. 30). The squirrel likely inhabited lowland forest in the Maros region before the landscape was transformed from forest to agricultural plains and may have been sympatric with Prosciurillus sp. during the 10,000–3,500-year interval. The large-bodied Rubrisciurus rubriventer also once occurred on the peninsula, documented by a subfossil cranial fragment (see account of R. rubriventer).

Fig. 33

Habitat of Prosciurillus murinus in tropical lowland evergreen rain forest at Kuala Navusu, 100 m. The large-bodied Rubrisciurus rubriventer and smaller-bodied Prosciurillus alstoni were encountered in the same forest. This habitat is similar to that south of Kuala Navusu along the Sungai Tolewonu where the same two species, along with the ground squirrel Hyosciurus ileile, were caught. Photographed in 1975.

Fig. 34

Habitat of Prosciurillus murinus in upper montane rain forest on Gunung Nokilalaki, 2200 m. The tree squirrel, Prosciurillus topapuensis, and ground squirrel, Hyosciurus heinrichi, also live here. See table 2 for range of ambient temperatures recorded during the sampling period. Photographed in 1975.

Archaeological remains of squirrels from caves at the tip of Sulawesi's southwestern peninsula are extremely rare. Of the more than 1000 specimens of mammals excavated from cave sites at the southern end of the southwestern peninsula during the 1900s (see Dammerman, 1939; Hooijer, 1950; Clason, 1976; Musser, 1984; Simons, 1997), only three squirrels have been noted. One was described by Sarasin (1905) as “Sciurus rubriventer?,” a cranial fragment excavated from cave sediments along with skeletal pieces of other mammalian species. The other two were excavated from sediments in Ulu Leang I, the dentary fragment of Prosciurillus we describe here and a “maxilla” listed in a table by Clason (1976: 66); she provided no details. We have not seen Sarasin's specimen, but his account clearly describes a Rubrisciurus rubriventer. Clason's material was excavated by Glover from Ulu Leang I mostly during 1973. We do not have access to those specimens. Our dentary fragment was found during Glover's 1975 excavation of the cave and sent to Musser along with other mammalian fragments.

Clason (1976: 66) tabulated more than 1000 mammalian cranial and postcranial fragments found by Glover in Ulu Leang I (no estimate of the actual number of individuals represented is available). Some were not yet identified at the time of her report, but 852 were given preliminary identifications. Of these, one represents a squirrel, 65 are from non-sciurid rodents, and the rest sample phalangers, bats, primates, carnivores, and artiodactyls. Non-sciurid rodents, especially those of large body size such as the species of Lenomys, Paruromys, and Taeromys are hunted today in other parts of Sulawesi; drift fences made of palm fronds are used with snares placed in openings along the drift fence (Musser's observations in central Sulawesi). Likely some of the rodent fragments from Ulu Leang I represent remnants of prehistoric human meals (see Musser, 1984); other pieces are probably from owl pellets, although some could be from the scat of the endemic Sulawesian civet Macrogalidia musschenbroekii. That carnivore may be represented by isolated teeth from Ulu Leang I (Clason, 1976) and skeletal fragments have been collected from other prehistoric cave sediments in the region (Hooijer, 1950). In the upper montane forest on Gunung Nokilalaki, Musser frequently saw Macrogalidia and found feces containing cranial and postcranial bits of the murid, Bunomys penitus, which is the most common small rodent in that forest.

In contrast to the murid rodents, all the endemic species of Sulawesi squirrels are diurnal and less exposed to owl predation, although some now and again are likely taken by hawks, eagles, and Macrogalidia. Squirrels are seen but rarely caught by the local people. According to the villagers Musser encountered in the forest, none had ever caught squirrels in their snares set along drift fences. Rather than running alongside a drift fence as rats do, squirrels would simply bound over it. Rats and mice can also be dug out of their burrows, but getting to nests of tree squirrels is more difficult. The prehistoric people living on the southwestern peninsula may have had equal difficulty in capturing squirrels, or it was simply more efficient in time and energy to hunt and capture larger mammals along with rats and mice.

The Prosciurillus murinus Group

Two species comprise this cluster, both the smallest in body size among all the tree squirrels and ground squirrels endemic to Sulawesi. One is Prosciurillus murinus, named and described by Müller and Schlegel in 1844, which has been collected from most of mainland Sulawesi where it occurs through an altitudinal gradient from coastal lowlands to mountains and within the range of forest formations from tropical lowland evergreen rain forest to upper montane rain forest; specimens were also taken from two small islands off the northeastern coast of the northern peninsula. The other is Prosciurillus abstrusus, named and described by Moore in 1958; it has only been collected at 1500 m and 2000 m in montane forest on Pegunungan Mekongga, the highest range on the southeastern peninsula of Sulawesi.

Although originally described as a species of Sciurus, the genus used for most new species of squirrels described during the 1800s and early 1900s, murinus was eventually transferred to Sciurillus (Ellerman, 1940: 318) then subsequently designated the type-species of Prosciurillus (Ellerman, 1947: 259) where it has remained (see table 34 and introduction to Prosciurillus).

TABLE 34

Allocation of Scientific Names Associated with Species in the Prosciurillus murinus Group as Presented in Primary Published Checklists of Mammals from 1940 to the Present Generic and specific names as originally published are listed in their published chronological order. See the species accounts for names of authors and dates of publication.

Three scientific names have been associated with murinus, one described as a separate species, the other two as subspecies of murinus; after 1947 all were either recognized as subspecies or synonyms (table 34). From our study of skins and skulls, we can delineate a single species, P. murinus, and similar kinds of data sources indicate P. abstrusus to be a separate but related species. Concordant with the morphological data identifying two distinctive species are their sucking lice parasites: each species of squirrel supports a distinctive species of Hoplopleura (see the descriptions of sucking lice).

Definitions of the species limits of P. murinus and P. abstrusus, based on qualitative evaluation of variation in coat color combined with morphometric analyses of cranial and dental dimensions, along with summaries of their geographic and altitudinal distributions derived from collection localities of voucher specimens, and contrasts between the two, are provided in the following accounts.

Gazetteer and Specimens Examined

Collection localities for the 197 specimens of P. murinus and the 30 examples of P. abstrusus studied are listed below. The number preceding each locality keys to a symgbol on the map in figure 30.

Prosciurillus murinus

1. Pulau Talise, 01°50′N, 125°03′E, sea level (highest point on island is 264 m): BMNH 87.7.15.1.

2. Teteamoet (several miles southeast of Likupang; see Raven's brief description of the place in Miller, 1917: 29), 01°40′N, 125°05′E (estimated from Raven's map), on coastal plain near sea level: USNM 216793–95.

3. Manado (also spelled “Menado”), 01°30′N, 124°50′E, coastal plain near sea level: ANZP 14156; BMNH 88.7.15.1, 97.1.2. 18; MZB 5975, 5978; RMNH 13216–18 (specimens “d–f” in Jentink's [1888: 22] catalog; specimen “e” is actually from “Ménado-Langowan).

4. Gunung Klabat (“Goenoeng Kalabat” on specimen labels), 01°28′N, 125°02′E: AMNH 196512 (“Koemersot,” 250 m on skin label); USNM 217809 (5600 ft [1707 m]). This specimen was collected by H.C. Raven, who provided this note (quoted in Riley, 1924: 1): “My camp was at about 1,700 meters (5,600 feet), where the forest is only semitropical in appearance. Practically all the trees are heavily coated with moss and are not tall. Kalabat is the highest mountain in Minahassa, having an altitude of 2,020 (6,617) feet.”

5. Pulau Lembeh, 01°26′N, 125°13′E (elevation of collection site is not recorded but highest point of the island is 447 m): BMNH 40.631, 40.632; SNSD 3081; USNM 217810–13, 217814 (holotype of Sciurus evidens), 217815.

6. Rurukan, 01°21′N, 124°52′E: AMNH 196510 (900 m), 196511 (1000 m); BMNH 97.1.2.17, no elevation is recorded for the specimen, but Rurukan is at 1000 m; Sheet NA 51-12).

7. Tonsealama (also known as “Tonsea”), 01°19′N, 124°55′E, 600–700 m (estimated from Sheet NA 51-12): MZB 5976, 5977.

8. Tomohon, 01°19′N, 124°49′E, 700–800 m (estimated from Sheet NA 51-12): BMNH 99.10.1.6. Meyer (1898: 21) reported specimens from Tomohon.

9. Temboan (on Kuala Kalait, “is a new clearing of eight houses and lies from Mt. Sapoetan south, 55° west and about six miles from Loboe,” wrote Raven in his field journal, 1916: 3 (in mammal division library, USNM), 01°03′N, 124°33′E (estimated from Raven's map), 500 m (estimated from Sheet NA 51-12): USNM 217816–21.

10. Amurang, 01°11′N, 124°35′E, on coastal plain near sea level: MZB 1502–1505.

11. Pinogu, Bone Valley (also spelled Pinogoe), 00°32′N, 123°25′E, 200 m (estimated from Sheet NA 51-14): BMNH 99.10.1.23.

12. Gorontalo, 00°31′N, 123°03′E, coastal plain near sea level: RMNH 13215 (specimen “c” in Jentink's [1888: 22] catalog).

13. Bumbulan, 00°29′N, 122°04′E, coastal plain near sea level: AMNH 152921, 152932, 152938–43, 153281, 153282; MZB 5973; RMNH 9827 (formerly MZB 5974; holotype of Sciurillus murinus griseus).

14. Sungai Paleleh (“I went inland about four or five miles over the mountains and made camp at the edge of the Paleleh River, which is a small brook … with steep mountains or hills on all sides” [Raven, in Miller, 1915: 23]), 00°59′N, 121°49′E (estimated from Raven's map), 700 m (estimated from Sheet NA 51-14): USNM 200275–78.

15. Matinan (also spelled Matinang), 01°05′N, 121°42′E (for village near coast; specimens came from highlands south of village in foothills of Pegunungan Peleleh at 600 m): AMNH 196513–19. Meyer (1898: 21) reported a specimen from “Matinangkette” (Matinan range, part of the larger Pegunungan Peleleh) at 1000 m.

16. Gunung Ile-Ile, 00°58′N, 121°48′E (part of the larger Pegunungan Peleleh forming the mountainous backbone of the northwestern portion of the northern peninsula): AMNH 196524–28 (500 m), 196520–23 (1700 m).

17. Valley of Sungai Miu, Sungai Oha Kecil (small tributary on left side of Sungai Miu), 01°22′S, 119°57′E (near confluence with Sungai Miu; estimated from Sheet SA 50-8), 290 m: AMNH 224589–91.

18. Sungai Oha Kecil, 1300 ft (396 m): AMNH 224592.

19. Sungai Oha Kecil, 1400 ft (427 m): AMNH 224593.

20. Sungai Oha Kecil, 1600 ft (488 m): AMNH 224594, 224595.

21. Valley of Sungai Miu, Sungai Miu (right side), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 350 m: AMNH 224046–49.

22. Valley of Sungai Miu, Sungai Sadaunta (also spelled “Sidaonta” or “Sidaunta”; tributary on right side of Sungai Miu), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 675 m: AMNH 224043–45.

23. Sungai Sadaunta, 2500 ft (762 m): AMNH 224601–603; 2550 ft (777 m), AMNH 224604.

24. Sungai Sadaunta, 2700 ft (823 m): AMNH 224596, 224597, 224605–607.

25. Sungai Sadaunta: 2800 ft (854 m), AMNH 224598, 224608, 224609; 2850 ft (869 m), AMNH 224610.

26. Sungai Sadaunta: 2900 ft (884 m), AMNH 224599, 224611.

27. Sungai Sadaunta: 3000 ft (915 m), AMNH 224600, 224612, 224613; 3050 ft (930 m), AMNH 226836.

28. Sungai Sadaunta, 3200 ft (976 m), AMNH 224614, 226837; 3250 ft (991 m), AMNH 224615.

29. Sungai Sadaunta, 3300 ft (1006 m): AMNH 224616.

30. Sungai Sadaunta, 3400 ft (1037 m): AMNH 224617.

31. Valley of Danau Lindu, Tomado (a village on western shore of Danau Lindu), 01°19′S, 120°03′E (estimated from Sheet SA 50-8), 1000 m: AMNH 223021, 223022, 223475, 224050, 224051.

32. Gunung Kanino, 01°17′S, 120°08′E (estimated from Sheet SA 50-8), 4600 ft (1402 m): AMNH 225492; 4650 ft (1418 m), AMNH 225493–96.

33. Gunung Kanino, 4750 ft (1448 m): AMNH 225499; 4800 ft (1463 m), AMNH 223536, 223538, 223539.

34. Gunung Kanino, 4900 ft (1494 m), AMNH 225500.

35. Gunung Kanino, 5200 ft (1585 m): AMNH 223537.

36. Gunung Nokilalaki, 01°13′S, 120°08′E, 7000 ft (2134 m): AMNH 225497; 7100 ft (2187 m), AMNH 223498.

37. Malakosa, Kuala Navusu, 00°58′S, 120°27′E (estimated from Sheet SA 51-1): 100 ft (30 m), AMNH 226063–66; 125 ft (38 m), AMNH 226067, 226068; 150 ft (46 m), AMNH 226069; 180 ft (55 m), AMNH 226070; 200 ft (61 m), AMNH 225909; 350 ft (107 m), AMNH 226071; 450 ft (139 m), AMNH 226072, 226073; 600 ft (182 m), AMNH 226074; 750 ft (229 m), AMNH 226075.

38. Tolai, Sungai Tolewonu, 01°04′S, 120°27′E (estimated from Sheet SA 50-8): 500 ft (152 m), AMNH 226500–502; 540 ft (166 m), ASE 4174; 600 ft (183 m), AMNH 226503, 226504; 650 ft (198 m), AMNH 226505; 700 ft (213 m), AMNH 226506; 750 ft (229 m), AMNH 226507; 800 ft (244 m), AMNH 226508; 1000 ft (305 m), AMNH 226509.

39. Pinedapa, 01°25′S, 120°35′E (estimated from Raven's map), 100 ft (31 m): USNM 219504–507, 219509.

40. Rano Rano 01°30′S, 120°28′E, 6000 ft (1829 m): USNM 219508, 219510.

41. Kulawi, 01°27′S, 119°59′E, 500 m: USNM 218713.

42. Gunung Lehio, 01°33′S, 119°53′E, above 6000 ft (1829 m): USNM 218712 (holotype of Sciurus murinus necopinus).

43. Wawo, on the plain between the coast and western foothills of Pegunungan Mekongga (also spelled “Mengkoka”), 03°41′S, 121°02′E, 50 m: AMNH 101390–93.

44. Pegunungan Mekongga, Masembo, which is southeast of Wawo and the highest place in the southern portion of Pegunungan Mekongga (see maps and discussion in Heinrich [1932] and Stresemann [1940]) 03°35′S, 121°15′E (for the Pegunungan), 550 m: AMNH 101379, 101394.

45. Pegunungan Takolekaju (“Molengraff Range,” the old the European name for the mountains, is notated on the specimen tags; no more precise collection locality is available; P. Jenkins, in litt., 2008), an extensive mountainous region in the western portion of the central core with the north-south boundaries between approximately 01° and 02°15′S, and extending slightly diagonally from about 119°45′E in the north to 120° near its southern ramparts: BMNH 40.636 (1500 ft, 457 m), 40.365 (3200 ft, 976 m), and 40.367 (3500 ft, 1067 m).

46. Pegunungan Latimojong, 03°30′S, 121°23′E, 2200 m: AMNH 196529–33.

47. Lombasang (also spelled “Lambasang”), northwest of Gunung Lompobatang, 05°16′S, 119°50′E, 1100 m: AMNH 101380–84, 101387–89.

48. Gunung Lompobatang (also spelled Lompobattang; see Fraser and Henson, 1996, for example; spelled “Pik v. Bonthain” or “Pik v. Bantaeng” on old maps), Wawokaraeng, 05°20′S, 119°55′E: 2000 m, AMNH 101385, 101386. Tasoso (spelled “Dasoso” on the skin tag; a village on the lower slopes and one of Alfred Everett's collection localities [see Hartert, 1896]); 05°17′S, 119°58′E, 4000 ft (1320 m): BMNH 97.1.3.9.

The following specimens were studied but the places where they were caught have not been mapped.

Prosciurillus abstrusus

1. Pegunungan Mekongga (also spelled “Mengkoka”), Tanke Salokko (the highest spot in Pegunungan Mekongga; see the maps and discussions in Heinrich [1932] and Stresemann [1940]), 03°35′S, 121°15′E (for the Pegunungan): 1500 m, AMNH 101350, 101351; 2000 m, AMNH 101349, 101352–77, 101378 (holotype of Prosciurillus abstrusus).

Prosciurillus murinus (Müller and Schlegel, 1844)

Sciurus murinus Müller and Schlegel, 1844: 87.

Sciurus murinus necopinus Miller and Hollister, 1921: 98.

Sciurus evidens Miller and Hollister, 1921: 99.

Sciurillus murinus griseus Sody, 1949: 77.

Lectotype and Type Locality

The lectotype of Prosciurillus murinus is an adult female (RMNH 13213, specimen “a” in Jentink's [1888: 22] catalog) obtained by E.A. Forsten sometime during 1840–1842. It consists of a skin mounted in a live pose and a damaged cranium, the latter also listed as specimen “a” in Jentink's (1887: 190) osteological catalog. The right zygomatic region is missing, the basicranial area is fragmented, the right bullar capsule is gone, and the cranium is cracked in several other places; both dentaries are missing. Values from dental and some cranial measurements are listed in table 35.

TABLE 35

Age, Sex, and External, Cranial, and Dental Measurements (mm) for Types of Prosciurillus murinus (includes necopinus and evidens), and Prosciurillus abstrusus

Specimen “a” was one of three specimens cataloged as types ( =  syntypes) by Jentink (1887: 190, 1888: 22). At Chris Smeenk's suggestion (in litt., 2008), we select specimen “a” as the lectotype following the rules promulgated in Article 74.1 of the Code (ICZN, 1999: 82); G.H.H. Tate had scribbled “lectotype” on the specimen tag during his visit to Leiden in 1951 (C. Smeenk, in litt., 2008). The other two specimens, collected by E.A. Forsten between 1840 and 1842, become paralectotypes: specimen “b” (Jentink, 1888: 22), RMNH 13214, is an adult male skin mounted in live pose with skull still inside the mount; the osteological specimen “c” (Jentink, 1887: 190), RMNH 13219, is a skull only. See the account of P. leucomus for a description of Forsten's travels through northeastern Sulawesi.

The type locality is “Nord de Célèbes,” as listed in Jentink's (1887: 190, 1888: 22) catalogs. Forsten obtained most of his material in the region near the tip of the northeastern peninsula, which is in the administrative district of “Minahasa” (Kabupaten Minahasa), between 1° and 2° N. Sody (1949: 77) restricted the type locality to “the extreme N.E. part of the island,” which effectively places the type locality in Kabupaten Minahasa, Propinsi Sulawesi Utara, Indonesia. However, the type locality should rather be defined as “NE Celebes” because Forsten also worked in the environs of Gorontalo and as far west as Paguat (September–November, 1841; see Van Steenis-Kruseman [1950: 179] and Forsten's unpublished diary in the archives of the Leiden Museum); hence, we cannot exclude that one of the specimens is from that region (C. Smeenk, in litt., 2008).

Emended Diagnosis

The smallest-bodied of the species of tree squirrels endemic to Sulawesi (see table 3), and further characterized by: (1) uniform dark brown upperparts flecked with buff, ochraceous, and black; (2) lack of ear tufts, nape patches, middorsal black stripe, or any other patterning formed by different colored stripes and patches; (3) dark grayish buff to ochraceous gray underparts; (4) tail that is shorter than length of head and body; and (5) small, gracile skull (figs. 12–Fig. 1314).

Geographic and Altitudinal Distributions

Except for the east-central peninsular region, collection localities for Prosciurillus murinus are scattered throughout mainland Sulawesi and are also from Talise and Lembeh islands off the coast of the northeastern peninsula (see gazetteer and map in fig. 30). Likely the species can be encountered anywhere on Sulawesi where forest persists, even the east-central peninsula, which has been poorly surveyed for small mammals, especially squirrels.

Prosciurillus murinus is found in forest formations ranging from tropical lowland evergreen rain forest throughout the coasts and middle altitudes to tropical upper montane rain forests in high mountains. On the northern peninsula, voucher specimens come from the coastal plain near sea level to 1700 m on Gunung Klabat and Gunung Ile-Ile, although most examples were collected at places that are scattered between the coastal plain and 1000 m. Kuala Navusu at 30 m and Gunung Latimojong at 2200 bracket the range of elevations at which samples of P. murinus have been obtained in the central core of Sulawesi. On the southwestern peninsula, specimens come from 1100 m (Lombasang) and 2000 m (Gunung Lompobatang). Before most of the peninsula was converted from forests to agriculture (see account of Prosciurillus sp.), P. murinus likely occurred in forests below 1100 m, down to and along the coastal plain.

Only two places on the southeastern peninsula have yielded voucher specimens: Wawo at 50 m near the coast and Masembo at 500 m inland, and this region forms an exception to the altitudinal range of P. murinus, extending from coastal plain to mountains, documented in the central core of the island and on the northern peninsula. Montane forests on Pegunungan Mekongga, the mountain range looming above Wawo and Masembo, support populations of P. abstrusus, a close relative of P. murinus; samples of the former are from 1500 and 2000 m. The lower altitudinal limit of P. abstrusus in this highland region and the upper limit of P. murinus are unknown.

Pulau Talisei, 8 km northeast of the northwestern tip of the Sulawesi mainland, and Pulau Lembeh, directly off the western coast of the northeastern mainland tip (see map in fig. 28), are the collection sites of the only two insular samples of Prosciurillus murinus. Another squirrel, P. leucomus, and several other native Sulawesi mammals are recorded from Pulau Lembeh (see the account of P. leucomus), but samples of only P. murinus and the macaque, Macaca nigra, come from Pulau Talisei. That island is separated from the mainland by two smaller islands and water depths of less than 50 m, mostly only 10 m (Sheet NA 51-12). As with Pulau Lembeh, Talisei was most likely part of mainland Sulawesi during Pleistocene glacial intervals when sea level was depressed by at least 120 m, and separated during warm inter-glacial periods (see the account of P. leucomus). Neither squirrel nor macaque exhibits any significant morphological contrasts with mainland samples, suggesting relatively recent isolation on Pulau Talisei.

Description

Müller and Schlegel (1844: 87) described murinus with this sentence (translated from the original Dutch by Chris Smeenk, in litt., 2008; see appendix 2 for a rendition of the text in Dutch):

Prosciurillus murinus is the smallest in body size of the species of tree squirrels endemic to Sulawesi (length of head and body, 102–150 mm; length of hind foot, 32–38 mm; weight, 42–110 g; extremes from table 36), and one of the smallest of the tree squirrels and ground squirrels that are native to the Indomalayan region. A few species of Sundaic Callosciurus (C. adamsi and C. orestes) and Sundasciurus (S. lowii, S. tenis, S. jentinki, and S. brookei) are similar to P. murinus in body size; only the species of pygmy tree squirrels in Nannosciurus and Exilisciurus are smaller (Medway, 1969; Heaney, 1985; Payne et al., 1985).

TABLE 36

Descriptive Statistics for Measurements (mm) of Lengths of Head and Body, Tail, Hind Foot, and Ear, and for Weight (g), Derived from Samples of Prosciurillus murinus and Prosciurillus abtrusus^a Mean ± 1 SD, observed range (in parentheses), and size of sample are listed. Mean values were used to compute LT/LHB. Specimens measured are listed in footnotes.^b

Uniformly dark upperparts, unbroken by contrasting ear tufts, nape patches, midventral black strip, or any other contrasting adornment, and grayish underparts characterize the small and dark P. murinus. The dense and short (8–10 mm thick in most specimens) fur covering the upperparts from nose to base of the tail, including the ears and all appendages, is dark brown flecked with buff or ochraceous tints and peppered with black, the middorsal region slightly darker than sides of the head and body. The dark hue, conspicuously darker than seen in species of the P. leucomus group or Rubrisciurus rubriventer, results from the overhairs that are dark gray for most of their lengths, have a subterminal buff or ochraceous band, and are tipped with black. No tufts or postauricular patches distinguish the small ears from the rest of the dorsum. The eyes are circled by buffy rings.

The dense and short (up to 5 mm thick) fur covering the underparts, from chin to base of the tail, ranges from dark gray washed with pale buff to dark ochraceous gray in most samples (hairs are dark gray for most of their length and tipped with buff or ochraceous tints); a few specimens have dark grayish white venters (tips of the hairs are unpigmented). Most specimens fall in the range between dark grayish buff and ochraceous gray. The demarcation between upperparts and underparts in the latter is not sharp; for example, USNM 219508 from Rano Rano has a solid dark ochraceous gray venter that inconspicuously merges with coloration of the dorsal coat.

The tail is shorter than the length of the head and body (LT/LHB  =  68%–86%, see table 36) with the same color pattern as the dorsal fur—long black hairs with alternating distal ochraceous and black bands. Hairs forming tip of the tail are all black.

Females exhibit three pairs of teats, just as in members of the P. leucomus complex: one postaxillary pair and two inguinal pairs. A single embryo was found in each of the few females examined.

Views of the small, gracile skull are illustrated in figures 12–Fig. 1314; summary statistics for cranial and dental measurements are listed in tables 37 and 38. Conformations of the skull and teeth are basically miniatures of those elements in the P. leucomus group.

TABLE 37

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Population Samples of Prosciurillus murinus Mean ± 1 SD and observed range (in parentheses) are listed.

TABLE 38

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Population Samples of Prosciurillus murinus, and from the Sample of Prosciurillus abstrusus Mean ± 1 SD and observed range (in parentheses) are listed.

Comparisons

Prosciurillus murinus is markedly smaller in body size than any other species of tree squirrel or ground squirrel endemic to Sulawesi except for the small-bodied P. abstrusus, which resembles P. murinus not only in body size but coat color. It is between these two that comparisons are required, which we document here.

Prosciurillus abstrusus is still known only by the original 30 specimens collected by Gerd Heinrich in 1932 at 1500 and 2000 m on Pegunungan Mekongga, the highest range on the southeastern peninsula of Sulawesi. In diagnosing the species, Moore (1958: 3) wrote that it “has short white pelage on the backs of the ears which distinguish it from skins of … Prosciurillus murinus; otherwise only size distinguishes the stuffed skins, P. abstrusus being larger than P. murinus. Moore also noted that P. abstrusus had underparts less intensely washed with buff or ochraceous hues.

Mean values of external measurements are greater when the large sample of P. abstrusus is contrasted with the very small sample of P. murinus from the lowlands of the southwestern peninsula, but such distinctions are not evident between P. abstrusus and the larger samples of P. murinus from the central core of Sulawesi and the northern peninsula (table 36). The pelage differences described by Moore, however, consistently distinguish the two species. Backs of the ears are covered with fine, short white hairs that form a white mat on all specimens of P. abstrusus, but we have not seen this pattern on any example of P. murinus—in that species, the fur covering the ears is the same color as the rest of the upperparts. Both P. abstrusus and P. murinus have similar dark brown dorsal fur in which the buffy or ochraceous hair tips provide a flecking over the dark brown background. The coat averages thicker in P. abstrusus compared with lowland samples of P. murinus (10–12 mm versus 8–10 mm, respectively), but is comparable in thickness to high mountain samples of P. murinus. All examples of P. abstrusus have dark grayish white venters (hairs are dark gray basally and unpigmented at their tips); some specimens show a pale buffy wash across the chest, and a few others have spots or larger patches of pale buff scattered over the venter. Most examples of P. murinus have brighter underparts, dark gray washed with buff or richer ochraceous tints; a few match the average in P. abstrusus—dark grayish white underparts.

While contrasts between the two species in lengths of head and body, tail, and hind feet are not impressive, P. abstrusus has an appreciably larger skull and longer tooth rows than does P. murinus. This difference can be appreciated qualitatively by visually comparing skulls of the two species side-by-side (figs. 12–Fig. 1314) and quantitatively by the contrasting mean values for cranial and dental dimensions summarized in tables 37 and 38. Nearly all cranial measurements average greater in the sample of P. abstrusus compared with P. murinus, and there is no overlap between the samples in the range of values for lengths of bulla and tooth row, and breadth of bony palate. A few dimensions are similar or smaller in P. abstrusus compared with P. murinus. Typically, the Mekongga squirrel has a relatively narrower interorbit, shorter nasals, rostrum, and diastema relative to occipitonasal length, and an absolutely shorter orbit.

The cranial and dental distinction between the two species is also reflected in the results of multivariate analyses of cranial and dental variables expressed by the distribution of specimen scores projected onto the first and second principal components extracted from principal-components analysis (fig. 31). The projection of scores along the first axis results in two discrete clusters, the one on the left representing all samples of P. murinus, that on the right signaling the larger specimens of P. abstrusus. Covariation in most dimensions influences this segregation of scores along the first principal component; lengths of bony palate, bulla, and tooth row along with breadths of rostrum and bony palate are especially strong (table 39). Prosciurillus abstrusus has relatively shorter nasals, rostrum, diastema, and orbit compared with P. murinus as indicated by their large and positive scores along the second axis, and relatively longer tooth rows as reflected by the large negative score for that dimension (table 39).

Fig. 35

Collection localities for samples of Hyosciurus heinrichi and H. ileile. Numbers key to localities described in the gazetteer where specimens are also identified by museum initials and catalog numbers. The inset map, right (rectangle in larger map, above), shows collection sites (1–12) for H. heinrichi scattered along Musser's transect over Gunung Kanino and Gunung Nokilalaki, and localities (4–9) for H. ileile lying along the Sungai Sadaunta and slopes of Gunung Kanino. The dashed contour line at 1300 m marks the approximate boundary between tropical lowland evergreen rain forest and tropical lower montane forest.

TABLE 39

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus murinus with the Sample of Prosciurillus abtrusus Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 31.

An osseous qualitative trait can be added to the absolute and proportional cranial dimensional differences between the two species. The smaller-bodied P. murinus has a conspicuously higher jugal component of the zygomatic arch, the dorsal border typically forming a high process. The larger-bodied P. abstrusus has a lower jugal, its dorsal border smooth or with only a low dorsal process (fig. 14).

Prosciurillus abstrusus inhabits montane forests on Pegunungan Mekongga where it replaces its close relative P. murinus. The latter was sampled by G. Heinrich in tropical lowland evergreen rain forest covering the foothills of the Pegunungan at Masembo, 550 m (four specimens), and on the coastal plain at Wawo, 50 m (two individuals). Color and length of the fur of these lowland samples closely resemble those in samples of P. murinus from lowlands elsewhere on Sulawesi; the ears of all, for example, are the same color as the neck and back, and the pelage is 8–10 mm thick. We could not quantify cranial differences between the two species because skulls of the six lowland specimens collected by Heinrich are too damaged to obtain complete sets of cranial measurements. The tooth rows, however, remain intact: mean and extreme values for the six (5.1 ± 0.06, 5.0–5.2 mm) are nested within the range of variation shown by this variable for P. murinus (5.2 ± 0.17, 4.7–5.6 mm, N  =  57) and not for P. abstrusus (6.2 ± 0.13, 5.9–6.3 mm, N  =  14).

At present, there is no information revealing how high P. murinus extends onto the mountain range or the lowest altitude to which P. abstrusus descends. We suspect the altitudinal ranges to be mutually exclusive, their boundaries approximately coinciding with the limits of lower montane forest and lowland evergreen rain forest. This altitudinal exclusion of P. murinus from a mountain range and its replacement at those higher altitudes by a different but closely related species is unique to the landscape of the southeastern peninsula. Elsewhere on mainland Sulawesi, populations of P. murinus occupy tropical lowland evergreen rain forests on the coastal plain, in middle-altitude hill forests, and up into the mountains where montane forest formations prevail.

Geographic Variation

In addition to murinus, three other scientific names have been attached to geographic samples of the species, diagnosed primarily by chromatic distinctions of the fur and a cranial measurement, diagnoses inferring the presence of detectable and possibly significant geographic variation within P. murinus. Our visual inspection of coat coloration combined with multivariate analyses of data derived from cranial and dental measurements in samples from throughout Sulawesi, however, do not reveal significant geographic variation in these features. Why we disregard the three scientific names (necopinus, evidens, and griseus) as identifying distinctive populations within P. murinus is detailed in the section covering synonyms. We explain here why we cannot, using the specimens at hand, identify diagnostic geographic subsets of the species.

In stark contrast to species in the Prosciurillus leucomus group, all samples of P. murinus closely resemble one another in body size (comparing adults; see table 36) and coloration of the fur covering upperparts and tail—all samples contain a small-bodied, dark squirrel with a tail shorter than the length of head and body. There is a difference in thickness of the dorsal coat that is correlated with altitude. The few samples from high mountains, those taken on Gunung Nokilalaki, Pegunungan Latimojong, and Gunung Lompobatang (see gazetteer and map in figure 30), for example, are inseparable in coat color from those collected at lower altitudes, but have a slightly thicker dorsal coat, up to 15 mm in the montane samples; 8–10 mm is the thickness typical of specimens collected in lowlands. But where samples are available from an altitudinal gradient, along Musser's transect from Sungai Oha Kecil at 290 m to Gunung Nokilalaki at 2187 m (see gazetteer and fig. 30), for example, the thicker coat gradually gives way to a shorter coat at the lower collection sites.

There is some geographic variation in coloration of the fur covering underparts of the head and body. Dark gray washed with buff predominates in most samples; others are slightly paler (dark gray tinged with buff) or exhibit a richer hue (dark gray washed with ochraceous). The latter characterizes some samples from the central core of Sulawesi but also a few samples from the northeastern peninsula; paler venters predominate in samples obtained from terrain between those regions. A gradation from grayish buff to ochraceous gray can even be found within a single population sample. While of potential interest to studies involving coat-color variation, we cannot resolve the chromatic differences we see into geographic patterns that might reflect populations with distinct genetic histories.

Our comparison of data derived from measuring cranial and dental dimensions reveals variation in these quantitative traits that is associated more with age within our adult category than with geographic provenances of the samples. Specimen scores derived from population samples (identified in table 1) and projected onto the first and second principal components extracted from principal-components analysis illustrated in figure 32 form, with an exception, a single constellation without significant substructure pointing to identifiable clusters bounded by particular geographic regions. Scores representing specimens from the northern peninsula, including Pulau Lembeh off the northeastern coast, comingle with those identifying individuals from the central core of Sulawesi. Covariation in most variables spreads the scores along the first principal component (table 40), a measure of size, reflecting both individual variation within an age class, and variation due to age (the range in age from young adults to old adults constitutes the samples). The only striking departure from a single constellation is the score representing the animal from Gunung Lehio, the holotype of necopinus, and the only sample collected from that mountain. Its position far to the left in the ordination reflects its smaller skull because the squirrel is younger relative to all the other specimens measured. Although the squirrel is clothed in adult pelage, the cheek teeth are slightly worn and the basisphenoid-presphenoid and basisphenoid-basioccipital sutures incompletely fused.

Fig. 36

Views of the skull and dentary of an adult male Hyosciurus heinrichi (AMNH 225478) from Gunung Nokilalaki (2287 m). Occipitonasal length  =  64.9 mm.

TABLE 40

Results of Principal-Components Analysis Contrasting Population Samples of Prosciurillus murinus Principal components are extracted from a covariance matrix of log-transformed values for 15 cranial and 1 dental variable; see figure 32.

Three samples we studied are not included in the principal-components analysis. Specimens from Wawo and Masembo in lowlands of the southwestern peninsula (see gazetteer) have badly damaged skulls and we measured only the lengths of maxillary tooth rows. Mean and extreme values for six specimens (5.1 ± 0.06, 5.0–5.2 mm) fall within the range of variation calculated for other geographic samples of P. murinus (see tables 37 and 38). We also measured length of the hind foot on the six dry skins (other body measurements recorded by the collector are unreliable and we could not obtain accurate values from the stuffed skins). The mean (33.5 ± 1.05 mm) and extremes (32–35 mm) are also comparable to the range in variation seen in other population samples of P. murinus (table 36).

Damaged, juvenile, or missing skulls also excluded samples from Pegunungan Latimojong (2200 m) in the central core of Sulawesi, and Gunung Lompobatang (2000 m) on the southwestern peninsula (Lombasang, 1100 m, Tasoso, 1320 m, and Wawokaraeng, 2000 m; see gazetteer and map in figure 30) from the multivariate analysis using all cranial variables. We did measure lengths of maxillary tooth rows. Two specimens from Pegunungan Latimojong (each with a tooth row of 5.5 mm), and eight specimens from Gunung Lompobatang (5.5 ± 0.15, 5.3–5.7 mm) average slightly greater than in other geographic samples of P. murinus (tables 37, 38). We detected no significant difference in coloration of fur between these highland samples and those from comparable altitudes in the central core and northern peninsula of the island, and saw no significant size or conformational distinctions when we compared, side-by-side, the few less damaged skulls with those in other geographic samples. We also obtained mean and extreme values for length of hind foot, which we measured on the dry skins and used as an estimate of body size. (The samples were collected by G. Heinrich and his values for length of head and body along with length of tail are suspect, and we could not remeasure accurately these dimensions on the skins). We measured four specimens from the Latimojong range (34.8 ± 0.50, 34–35 mm) and 10 from the Lompobatang volcano (35.6 ± 0.52, 35–36 mm), which are comparable to the ranges of variation calculated for other population samples of P. murinus (table 36).

The pattern of geographic variation in traits associated with coloration of fur and cranial and dental dimensions obtained from samples of P. murinus collected from most of Sulawesi is similar to the pattern derived from samples of Rubrisciurus rubriventer. Individuals of P. murinus, the smallest-bodied of the endemic Sulawesian tree squirrels, and R. rubriventer, the largest Sulawesi tree squirrel in body size, are instantly recognizable wherever they are encountered on the island. Unlike species in the P. leucomus group where particular color patterns, along with average morphometric distinctions, are tied to different regions of mainland Sulawesi—P. leucomus on the northern peninsula, P. topapuensis in the highlands forming the western mountain block in the central core of the island, P. alstoni occurring over the eastern part of the central core and on the southeastern peninsula, and P. weberi at the lower end of the central core—no patterns of pelage color and morphometric variation in cranial and dental variables concordant with geographic regions characterize the available samples of P. murinus and R. rubrisciurus.

Ecology

The diurnal and arboreal Prosciurillus murinus is common in understory habitats of primary forest that bracket the range from lowland evergreen rain forest habitats (figs. 8, 22, 23, 33) to montane landscapes (figs. 27, 34, 41, 42), and warm to cool ambient temperatures (table 2); forests along streams, on hillsides, and on ridgetops were all occupied. Musser saw or heard P. murinus in the crowns of understory trees, low on the large trunks of high canopy and emergent trees, traveling over trunks and limbs on the forest floor, or foraging on the ground. The squirrels use the limbs and branches of understory trees and their attached woody vines as pathways through the understory canopy. On the ground they dash along tops of trunks and limbs lying in undergrowth on the forest floor, or dart from beneath one rotting tree trunk or pile of limbs to another. Many squirrels were trapped on tree trunks and limbs lying across streams and ravines (see summary of trapping sites in table 41). Musser saw one squirrel about 40 ft from the ground on the trunk of a canopy tree, but never noticed them any higher. The squirrels may forage into the upper canopy level and crowns of emergent trees, but they move very quickly, and would be difficult to locate unless moving slowly while concentrating on foraging.

Fig. 37

Views of the skull and dentary of an adult male Hyosciurus ileile (AMNH 226498) from Sungai Tolewonu (290 m). Occipitonasal length  =  63.1 mm.

Fig. 38

Specimen scores representing population samples of Hyosciurus heinrichi (filled circle, Gunung Kanino and Gunung Nokilalaki; N  =  35) and H. ileile (filled triangle, Sungai Sadaunta, Gunung Kanino, and Sungai Tolewonu; N  =  11) projected onto the first and second principal components extracted from principal-components analysis. Each ellipse outlines 95% confidence limits for specimen scores of each cluster. Equations for the regression lines are: H. ileile, Y  =  −0.121X+0.095 (F  =  3.20, P  =  <0.10); H. heinrichi, Y  =  −0.213X−0.033 (F  =  18.96, P  =  <0.001). The regression lines of the second principal component on the first are unambiguously distinct: their Y-intercepts are significantly different (+0.095 versus −0.033; F  =  15.38, P  =  <0.001), but not their slopes (−0.121 versus −0.213; F  =  1.16, P  =  0.288). The distribution of scores along the first axis is strongly influenced by length of tail, and the single point for H. ileile and the two for H. heinrichi situated far to the left of the main clouds of scores represent specimens with the shortest tails in the samples; the tails are naturally short, not damaged in traps or mangled by a predator and subsequently healed. Data were derived only from specimens captured and measured by Musser. See table 46 for correlations and percent variance.

TABLE 41

Summary of Habitat at Trapping Sites, Stomach Contents, and Other Relevant Information for Specimens of Prosciurillus murinus Collected by Musser in Central Sulawesi, 1973–1976 Collection locality, specimen number, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). Six of the collection localities (Sungai Oha Kecil, Sungai Miu, Sungai Sadaunta, Tomado, Kuala Navusu, and Sungai Tolewonu) are in tropical lowland evergreen rain forest; lower montane rain forest describes the places on Gunung Kanino, and Gunung Nokilalaki is mantled in tropical upper montane rain forest. With exceptions as indicated, all squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

In contrast to the wary and quiet Rubrisciurus rubriventer, a relative giant inhabiting the same understory habitats as P. murinus, the diminutive squirrels are aggressively vocal and not shy. Musser frequently encountered them when checking his traps. Once the squirrels detected his presence they became agitated, scolding from the ground hidden in the undergrowth, from looping woody vines and crowns of small trees, or on the lower trunks of the large canopy formers and emergents. Usually Musser heard the squirrels but could not see them. Those exposed on large tree trunks would soon tire of the confrontation and scurry down the trunk to the ground where they disappeared from sight in the undergrowth. Musser never saw a squirrel run up the trunk into the upper canopy. Vocalizations within the context of these interactions ranged from high-pitched chucks to almost whistles, to bird-like stacatto trills. Durden sometimes saw P. murinus in Bogani Nani Wartabone (then Dumoga-Bone) National Park in northern Sulawesi. As he sat quietly on a log removing ectoparasites from anaesthetized forest rats, individual P. murinus would occasionally descend to nearby tree trunks and chatter at the human intruder.

Musser occasionally saw P. murinus foraging on the ground but mostly in crowns of understory trees or on surfaces of large trunks. Two instances are illustrative. About 30 minutes before dark in lower montane rain forest on Gunung Kanino at 1500 m, Musser watched a squirrel working about 40 ft from the ground in the canopy of a small tree. The squirrel was moving head-first down a tree limb, its body pressed against the bark. It climbed over the lower branches and trunk in slow, jerky movements with its muzzle against the bark and appeared to be scoring the bark or digging into it. The squirrel would cover 2 ft of bark this way, then scamper to another part of the tree and work another section. Musser could not determine whether the squirrel was after a substance in the bark or listening for the movement of insect larvae beneath it.

Another time at about 4:00 p.m., Musser watched three squirrels foraging in the crowns of understory figs that canopied a section of the Sadaunta stream in lowland evergreen rain forest at 800 m. Each squirrel crawled along a branch with its body appressed against the bark, head down. The tail would alternately be held flat out, then quickly twitched upward towards the head, the motion accompanied by a bird-like, loud chirp. As the squirrels crawled along the branch, they occasionally stopped and dug their incisors into the bark, then moved on. They worked along a large branch to where it divided into smaller limbs, then jumped to other branches and began again to crawl and gnaw. The three worked over the branches for about 30 minutes, continually flagging their tails and chirping as they went, and occasionally emitting series of deeper chucks and chirps similar to the alarm call. None showed any aggression toward the other; often two would approach one another on the same branch, one working along the top of the limb, the other crawling on the limb's undersurface, passing by and continuing on.

Stomach contents reveal a diet of soft fruits, seeds, and insects (tables 41, 57). Some stomachs contained unidentifiable brown or tan fruit mash from soft fruits; others had remains of figs (the tissuelike endosperm, rubbery rind, and tiny seeds) and large, hard pyramidal seeds from another kind of fruit. Insects recovered from stomachs consisted of macrolepidopteran larvae (caterpillars); geometrid larvae (inch-worm moths); a primitive group of scale insects (Coccoidea, Sternorrhyncha, Margarodidae); arboreal termites (workers and soldiers in Termitidae); small adult beetles (represented by elytras, sclerite fragments, wings, legs, and antennal segments); large adult beetles chopped into pieces; larvae of buprestid beetles (small to large instars); and other kinds of beetle larvae, cockroaches, and cranefly larvae (Tipulidae). Both groups of caterpillars feed on foliage. All the scale insects found are sessile females. Appressed to the surface of bark and leaf stems, they feed by embedding their mouthparts into the vascular system of the tree. Nests of termites are attached to limbs and smaller branches. The buprestid larvae reside beneath bark, other kinds of beetle larvae could be in decaying sections of limbs or beneath bark, and adult beetles roam over surfaces of leaves and bark. The dipteran tipulid larvae live in damp soil, very decayed leaf litter, or very rotting wood on the ground (D. Grimaldi, personal commun., 2009). Cockroaches occur at all levels in the forest.

Some stomachs contained mostly fruit with only a few insects; others were packed with remains of caterpillars, scale insects, or termites along with a bit of fruit. The small caterpillars and beetle larvae were ingested whole, the larger species were usually chewed into pieces; scale insects were either intact or had been rendered into chewed fragments. Adult beetles were always represented by chewed fragments in the stomachs. The squirrels glean the caterpillars from the leaves, pick off the scale insects from surfaces of branches, scratch the termite nests and grab the insects as they pour out, dig into bark for the beetle larvae, and snatch adult beetles and cockroaches from leaves and tree limbs. On the ground they would scratch out the tipulid larvae, and also pick off any adult beetles or cockroaches encountered.

Musser caught only one squirrel in a live-trap. It ignored all foods offered and was released the next day.

Ectoparasites

A sucking louse Hoplopleura murinus, n. sp. (see following section for description), uniquely parasitizes Prosciurillus murinus (table 56). This small-bodied squirrel is also the host for two species of flea (Siphonaptera, Pygiopsyllidae): Farhangia quatturordecimdentata is recorded from voucher hosts collected at Tomado and Sungai Oha Kecil in central Sulawesi (Mardon and Durden, 2003), and F. celebensis was found on hosts obtained from Pulau Lembeh off the northeastern coast of the northern peninsula (Ewing, 1924; Traub, 1980). Farhangia quatturordecimdentata is also parasitic on the arboreal murid rodent, Margaretamys beccarii, another Sulawesian endemic confined to lowland tropical evergreen rain forest (Musser, 1982), but Farhangia celebensis is known only from Prosciurillus murinus (Mardon and Durden, 2003). Farhangia spp. are “nest fleas” (Traub, 1980) and would therefore be expected to be more common in nests of P. murinus than on the host. Ectoparasitic laelapid mites were recovered from P. murinus pelt AMNH 224589 collected at Sungai Oha Kecil in central Sulawesi in 1974 at an elevation of 290 m.

Sympatry

Over mainland Sulawesi, the geographic range of P. murinus overlaps those of Rubrisciurus rubriventer, both species of Hyosciurus, and all species of Prosciurillus except for P. abstrusus (table 6). Prosciurillus murinus and P. leucomus are also sympatric on Pulau Lembeh, off the coast of the northeastern peninsula (table 5). Along his transect in the northern portion of central Sulawesi, Musser trapped P. murinus in the same traplines, and sometimes in the same traps, as the tree squirrels R. rubriventer, P. topapuensis, P. alstoni, and the ground squirrels H. heinrichi and H. ileile (see table 41).

Synonyms

Information covering the three synonyms of P. murinus, and reasons behind their allocations are summarized below.

Sciurus murinus necopinus Miller and Hollister, 1921: 98. HOLOTYPE: USNM 218712 (museum study skin and complete skull; measurements are listed in table 35), a very young adult male collected by H.C. Raven (original number 3107) on January 20, 1917. TYPE LOCALITY: Gunung Lehio, 01°33′S, 119°53′E, above 6000 ft (1829 m; locality 42 in gazetteer and map in figure 30), in the western portion of the central core of Sulawesi, Propinsi Sulawesi Tengah, Indonesia.

Based on nine specimens from Gunung Lehio, Kulawi, Pinedapa, and Rano Rano in the central core of Sulawesi, Miller and Hollister (1921: 98) diagnosed necopinus as “Like Sciurus murinus murinus Müller and Schlegel, from Menado, North Celebes, but skull with decidedly smaller auditory bullae.” After presenting measurements, they remarked (p. 99) that “This subspecies reaches its extreme form in the high mountains of the interior of Middle Celebes. Specimens from Pinedapa near the coast of the Gulf of Tomini, near Mapane, show an approach toward the typical race of North Celebes.”

For Miller and Hollister, the name necopinus identified USNM samples from the central core of Sulawesi. Multivariate analyses of cranial and dental variables, which includes an estimate of bullar size, for the USNM specimens examined by Miller and Hollister and those collected by Musser along his transect from lowlands at the Sungai Oha Kecil to the highlands of Gunung Kanino and Gunung Nokilalaki (see tables 37 and 38), did not separate the central Sulawesian samples from those collected on the northern peninsula, the northeastern tip, or Pulau Lembeh (see map in fig. 30). In the graph of specimen scores projected onto the first and second principal components extracted from principal-components analysis illustrated in figure 32, the only striking departure from a single constellation of scores is the score representing the animal from Gunung Lehio, the holotype of necopinus. Its position far to the left in the ordination (table 40) reflects its smaller skull because the squirrel is younger relative to all the other specimens measured. Although clothed in adult pelage, the cheek teeth are slightly worn and the basisphenoid-presphenoid and basisphenoid-basioccipital sutures are open.

Squirrels in some samples from the central core of Sulawesi tend to have darker underparts (a rich ochraceous gray) than samples from other geographic regions, but there is geographic overlap in this chromatic feature. The series from Teteamoet in the northeastern limb of the northern peninsula, for example, is inseparable from the richly pigmented specimens collected at Pinedapa in the central core of the island.

We have not uncovered unique chromatic or morphometric traits identifying samples from the central core of Sulawesi as representing a population significantly different from that ranging over the northern peninsula and on Pulau Lembeh.

Sciurus evidens Miller and Hollister, 1921: 99. HOLOTYPE: USNM 217814 (museum study skin and complete skull; see table 35 for measurements), an adult female collected by H.C. Raven (original number 3176) on August 23, 1917. TYPE LOCALITY: Pulau Lembeh, 01°26′N, 125°13′E (elevation of collection site is not recorded but highest point of the island is 447 m; locality 5 in gazetteer and map in figure 30), of the coast of the northeastern end of the northern peninsula of Sulawesi, Propinsi Sulawesi Utara, Indonesia.

“Like Sciurus murinus Müller and Schlegel, from the mainland of Celebes, but paler, decidedly more yellowish or rusty brown” is how Miller and Hollister (1921: 99) diagnosed evidens based on six specimens from Pulau Lembeh. They remarked that “The paler, more yellowish brown coloration of this form makes the animal conspicuously different from the dark, richly colored Sciurus murinus of the neighboring mainland of Celebes.”

We examined all of Miller and Hollister's specimens from Pulau Lembeh and the adjacent mainland and failed to see their diagnostic chromatic distinction between island and mainland samples. Covariation in cranial and dental dimensions also do not result in two separate clusters of specimen scores projected onto first and second principal components extracted from principal-components analysis (fig. 32, table 40). Scores representing specimens in the type series of evidens are scattered throughout the compact constellation of points for squirrels in our samples from the northern peninsula and central core of Sulawesi. We have no evidence to indicate that the squirrels collected by Raven on Pulau Lembeh represent anything other than an insular population of Prosciurillus murinus, an assessment made earlier by Ellerman (1947: 259): “A specimen of Prosciurillus evidens Miller and Hollister, from Pulau Lembeh off North Celebes has been received at the Museum, and I consider it to be a synonym of P. murinus.”

Sciurillus murinus griseus Sody, 1949: 77. HOLOTYPE: RMNH 9827 (formerly MZB 5974; museum study skin, skull missing; skull and mandible were at Leiden in 1951 when G.H.H. Tate photographed them, but both elements cannot now be located in the collection; C. Smeenk, in litt., 2008), an adult female collected by J.J. Menden on October 24, 1939. TYPE LOCALITY: Bumbulan, 00°29′N, 122°04′E, coastal plain near sea level (locality 13 in gazetteer and map in figure 30), on the southern coast of the northern peninsula of Sulawesi, Propinsi Sulawesi Utara, Indonesia.

In addition to the holotype, Sody studied two other females collected by Menden from Bumbulan. Those three are part of a larger sample from Bumbulan obtained by Menden in 1939, ten of them currently stored in AMNH (see gazetteer). Sody (1949: 77) diagnosed griseus this way:

In our samples of P. murinus from throughout Sulawesi, the underparts range from dark gray speckled with white or pale buff to dark ochraceous gray, with most specimens falling within the range between dark grayish buff and ochraceous gray. The specimens from Bumbulan, including the holotype of griseus, fall close to the dark grayish buff end of the spectrum and in this respect are inseparable from some samples collected at places in the northern, central, and southeastern regions of the island.

We could not measure the skull from the holotype of griseus, but did obtain values for cranial and dental dimensions from four intact adult skulls in Menden's sample from Bumbulan housed at AMNH (the other six were so damaged by shotgun pellets that we could not obtain a full set of measurements). In the graph of specimen scores projected onto the first and second principal components extracted from principal-components analysis shown in figure 32, scores for the four specimens from Bumbulan (indicated by delicate arrows) are clumped with scores representing squirrels from the central core of Sulawesi, the northern peninsula, and the northeastern arm.

The sample from Bumbulan does not depart in any significant way from the extent of variation in color of underparts and dimensions of the skull and tooth rows expressed by other geographic samples of P. murinus.

Prosciurillus abstrusus Moore, 1958

Holotype and Type Locality

The holotype of Prosciurillus abstrusus is an adult female (AMNH 101378) collected by Gerd Heinrich on January 4, 1932. A stuffed museum study skin and accompanying skull comprise the holotype. The skin is intact as is the cranium and the mandible; all teeth are present.

The type locality is Tanke Salokko, 1500 m, a high place on Pegunungan Mekongga, a mountain range in the southeastern peninsula of Sulawesi (see the maps and discussions in Heinrich [1932] and Stresemann [1940], and locality 1 in the gazetteer and map in figure 30), 03°35′S, 121°15′E (for the Pegunungan), Propinsi Sulawesi Tenggara, Indonesia.

Emended Diagnosis

A small-bodied tree squirrel that in its morphology is most like Prosciurillus murinus among nannosciurine squirrels, but differs in having slightly duller upperparts and underparts, medial surfaces of the ears covered with white fur (but not extending beyond the pinnae rims to form tufts), absolutely larger skull, and relatively shorter rostrum but longer tooth rows (see section on comparisons).

Geographic and Altitudinal Distribution

This squirrel is known only from Pegunungan Mekongga where it was collected at 1500 m and 2000 m, elevations that bracket the transition between lower and upper tropical montane forest formations. Collections from lower elevations in tropical lowland evergreen rain forest in the foothills of Pegunungan Mekongga at 550 mm (Masembo) and on the coast 50 m (Wawo) between the Pegunungan and coast contained only Prosciurillus murinus.

Our knowledge of the montane fauna on Pegunungan Mekongga comes from the collecting efforts of G. Heinrich, his wife, and her sister at Tanke Salokko in 1932. Heinrich hunted birds and squirrels, his wife and sister trapped rats. Their samples of rats contained three species endemic to the mountain range and three others that are also found elsewhere. Taeromys arcuatus (collected at 1500 and 2000 m) and T. microbullatus (1500 m), along with Rattus salocco (1500 m), a member of the Rattus xanthurus group of species (Musser and Carleton, 2005), are, like the tree squirrel Prosciurillus abstrusus, endemic to the mountain range (Musser, ms). Samples of four other species of murid rodents—Bunomys chrysocomus, B. penitus, Paruromys dominator, and Rattus hoffmanni—were trapped at 1500 and 2000 m. Bunomys chrysocomus, Paruromys dominator, and Rattus hoffmanni also range into the lowland forests at the base of the Mekongga range and are found throughout Sulawesi; Bunomys penitus is restricted to montane forest habitats and also occurs on the western mountain block of Sulawesi's central core (Musser and Holden, 1991; Musser and Carleton, 2005; Musser, ms).

Maxomys dollmani is another rat found at Tanke Salokko along with Prosciurillus abstrusus. Unlike the tree squirrel, however, the distribution of M. dollmani extends to the central part of the west-central region in the central core of Sulawesi where it is represented by a single specimen (Musser, 1969). Prosciurillus murinus occurs throughout that western mountain block, but P. abstrusus does not.

Description

Prosciurillus abstrusus is one of the smallest-bodied of the species of tree squirrels endemic to Sulawesi (length of head and body, 115–148 mm, length of hind foot, 35–38 mm; extremes from table 36), matched only by P. murinus in external dimensions (length of head and body, 102–150 mm; length of hind foot, 32–38 mm; extremes from table 36). The moderately thick coat (12–15 mm) clothing upperparts of head and body is dark brown flecked with pale buff; the ventral fur is dark grayish white with a pale buff wash over the chest on some specimens. The tail is shorter than the length of the head and body (LT/LHB  =  81%) and the same color as the upperparts. Backs of the ears are densely covered with fine white hairs, forming a conspicuous white patch and providing the only contrast to the dark brown dorsum.

Females have three pairs of teats, one postaxillary pair and two inguinal pairs, the same combination possessed by all species of Prosciurillus.

Views of the small skull are illustrated in figures 12–Fig. 1314, where it is compared with skulls from other species of Prosciurillus; cranial and dental measurements are summarized in table 38.

Comparisons

Prosciurillus abstrusus is most closely related to P. murinus and the two species are contrasted in the account of the latter.

Geographic Variation

This aspect is not possible to document at the present time because samples of P. abstrusus have been collected at only two elevations in one small area (Tanke Salokko) of the elongate Mekongga range.

Ecology

No information is available covering these topics. Elsewhere on mainland Sulawesi, 1500 m, the lowest collection locality for P. abstrusus, would be in lower montane forest and 2000 m, the highest place where the species was obtained, would mark the beginning of the upper montane forest zone.

Ectoparasites

The sucking louse, Hoplopleura abstrusus, n. sp., uniquely parasitizes Prosciurillus abstrusus (see descriptions of lice in the following section). Also, ectoparasitic laelapid mites were recovered from six P. abstrusus pelts (AMNH 101353, 101355, 101357, 101359, 101361, and 101363), all collected at Tanke Salokko, Pegunungan Mekongga in southeastern Sulawesi at an elevation of 2000 m in 1931.

Sympatry

Prosciurillus abstrusus is the only squirrel that has been collected from the high reaches of Pegunungan Mekongga (tables 3, 5). It is replaced at lower elevations by its close relative, P. murinus (see that account). The only other member of Prosciurillus recorded from the southwestern peninsula is P. alstoni, a member of the P. leucomus group of species. It has been collected in the foothills of Pegunungan Mekongga at Masembo (550 m) and Mowewe (500 m) and at lower elevations on the western coastal plain at Wawo (50 m) and Lalolei (300 m). Samples of both P. alstoni and the smaller-bodied P. murinus have been taken at Masembo and Waso.

The large-bodied Rubrisciurus rubriventer has also been collected on the southeastern peninsula. Specimens are from Masembo, Wawo, and Lalolei, and from the slopes of Pegunungan Mekongga at 600 m and 1400 m. Whether the altitudinal ranges of P. abstrusus and R. rubriventer overlap between 1400 m and 1500 m or the distribution is parapatric in pattern is unknown.

Synonyms

No scientific name has been applied to a sample of P. abstrusus in the context of identifying a separate taxon. As part of his report on relationships among living members of Sciurinae, which was based on a survey of cranial traits, Moore (1959: 203) listed a specimen of “Prosciurillus obscurus” used in his synoptic set of specimens. The individual (AMNH 101354) is an example of P. abstrusus, and “obscurus” was simply a lapsus; the name has no nomenclatural status except as a nomen nudum.

Hyosciurus Archbold and Tate, 1935

“On the basis then of the extreme length of the nasals of old adults, the shortness of the tail, the long narrow foot, and the pronounced elongation of the claws,—this last perhaps in relation to a shift from arboreal to terrestrial or even semi-fossorial habits—it has seemed advisable to set up a separate genus, which may be named Hyosciurus,” was Archbold and Tate's (1935: 2) introduction to their description of this remarkable tropical ground squirrel:

The holotype and two other specimens were collected by G. Heinrich from Pegunungan Latimojong in central Sulawesi (see gazetteer), and the species was named in his honor, H. heinrichi. Heinrich had also collected two long-nosed squirrels from Gunung Ile-Ile in the northern peninsula of Sulawesi and these were also identified as H. heinrichi by Archbold and Tate (1935). A year later, however, Tate and Archbold (1936: 1) described the sample from Gunung Ile-Ile under the name ileile and arranged it as a subspecies of H. heinrichi. The perception of one species of Hyosciurus with a subspecies occurring on the northern peninsula and another in the central core of Sulawesi persisted (Ellerman, 1940; Laurie and Hill, 1954) until Musser caught squirrels with both morphologies in the northern portion of central Sulawesi, heinrichi in the mountains and ileile in the lowlands with the two distributed parapatrically at middle elevations (Musser, 1987). Primary checklists of mammals published after 1987 have recognized the two species (Corbet and Hill, 1992; Hoffmann et al., 1993; Thorington and Hoffmann, 2005).

Archbold and Tate (1935) thought Hyosciurus to be structurally similar to the long-nosed Rhinosciurus laticaudatus found on the Malaya Peninsula, Sumatra, Borneo, and some smaller islands on the Sunda Shelf (Corbet and Hill, 1992: 302). Ellerman (1940: 398) also compared Hyosciurus with Rhinosciurus but at the same time signaled their trenchant cranial differences, and later, in his volume on additions and corrections to the 1940 treatise (Ellerman, 1949: 14), noted that:

Ellerman's view was supported by diagnostic cranial traits described by Moore (1959) that in his view consolidated the Sulawesian Hyosciurus, Prosciurillus, and Rubrisciurus into a natural group, the subtribe Hyosciurina of tribe Callosciurini; Rhinosciurus was placed in subtribe Callosciurina, which contained most of the other Indomalayan genera. For Moore (1959: 175), “Ellerman … noted the important difference between Hyosciurus and Rhinosciurus and quite rightly inferred that they acquired their specializations of extremely long noses separately.”

Other researchers disagreed. In the early 1940s, Zahn (1942: 116) promulgated the opinion, which was extreme at the time, that Sulawesian heinrichi was simply a species of Sundaic Rhinosciurus. In the 1990s, Zahn's assessment was given a degree of legitimacy, for Corbet and Hill (1992: 301) allowed that “Hyosciurus should perhaps be included” in Rhinosciurus and pointed out that both species of Hyosciurus (p. 302) “have the hair in the mid-line of the nape reversed, often followed by a median parting of hair, about 3–4 cm long, between the shoulders, a condition shared only by Rhinosciurus amongst Indomalayan squirrels.”

Judged from analysis of molecular data, the shared protracted muzzle and reversed nape fur shared by Hyosciurus and Rhinosciurus do not signal close phylogenetic affinity—but instead, independently acquired morphologies associated with the evolution of long-nosed ground squirrels in tropical Asian rain forests. Analyses of the nuclear IRBP and mitochondrial 12S and 16S ribosomal DNA used by Mercer and Roth (2003) recovered a squirrel phylogeny that included a monophyletic group containing Rubrisciurus, Prosciurillus, and Hyosciurus separate from a cladistic cluster formed by Callosciurus, Rhinosciurus, and their relatives (see section on classification). Within the Sulawesian clade, Rubrisciurus is more closely related to the species of tree squirrels in Prosciurillus than to the morphologically divergent ground squirrels in Hyosciurus. The results from this molecular inquiry unambiguously support the hypotheses presented by Ellerman (1949) and Moore (1959) and not the assessments of Zahn (1942) or Corbet and Hill (1992).

Previously published descriptions defining Hyosciurus are incomplete or inaccurate so we provide here an emended generic diagnosis. The following combination of traits will distinguish Hyosciurus from other nannosciurine genera (see comparative measurements summarized in table 3, and compare skulls illustrated in figures 6, 12–Fig. 1314, 36, 37): (1) diurnal and terrestrial; (2) elongate muzzle; (3) dark brown upperparts flecked with buff and black, without ear tufts, nape patches, or dorsal stripes, but with hair reversed on nape followed by a median parting for 10–40 mm; (4) underparts completely white or cream, or with white or cream swath marked by dark brownish gray strips and patches, or broken into segments separated by brownish gray ventral fur; (5) tail short, slightly less than half the length of head and body; (6) hind feet long and slender; (7) claws very long relative to length of foot (25%–35% the length of the front foot) and only slightly shorter than the digits, thin, and slightly curved; (8) three pairs of teats (one abdominal and two inguinal); (9) rostrum elongate, nasals longer than width of interorbital region, as long as frontals in H. heinrichi but shorter than frontals in H. ileile (nasals 83%–86% of length of frontals), nasals and premaxillaries project well beyond anterior faces of upper incisors to form a short tube; (10) orbit short (indicated by lacrimal and posterior margin of zygomatic plate even with second upper molar); (11) posterior processes of the frontals about even with posterior wall of suborbit (the space between postorbital process and braincase); (12) jugal component of zygomatic arch low relative to size of skull; (13) low temporal ridges meet and fuse in adults 3–5 mm before occiput to form a short and wide sagittal crest (about 15% of parietal length); (14) anterior opening of the infraorbital canal lies far posterior to the premaxillary-maxillary suture (a reflection of the protracted rostrum), is not concealed by a bony flange of the ventral zygomatic root, the anteroventral lip of the canal is thick (almost forming a large tubercle), and the outer surface rough for insertion of the superficial masseter; (15) no transbullar septa (see Moore, 1959); (16) pterygoid fossa narrow and shallow in H. heinrichi, its lateral margin outlined by a low, inconspicuous ridge (the “ectopterygoid ridge” of Moore, 1959, which he thought was absent from skulls of Hyosciurus); (17) posterior border of bony palate even or slightly posterior to caudal margins of third molars; (18) descending palatine vein typically transmitted through a foramen (posterior maxillary foramen) at the posterolateral margin of bony palate just caudad and slightly medial to end of tooth row; (19) braincase shorter relative to skull length (as measured by PPL/ONL: 40% for Rubrisciurus; 38%–40% for species in the P. leucomus group; 37% and 35% for P. murinus and P. abstrusus, respectively; 32% and 33% for Hyosciurus heinrichi and H. ileile, respectively; computed from means listed in tables of measurements); (20) upper incisors orthodont in configuration relative to the rostrum (emerging from the rostrum at a right angle); (21) maxillary tooth rows parallel; (22) third upper premolar present, fourth premolar and first and second molars wider (labial-lingual distance) than long (anterior-posterior length), third molar nearly circular in coronal view (about as wide as it is long).

Hyosciurus shares number of teats with Prosciurillus (both have three pairs, including two inguinal pairs, but the anterior pair is postaxillary in position in Prosciurillus, not abdominal as in Hyosciurus); a short orbit, parallel maxillary tooth rows, third upper premolar, and fourth premolar and first and second premolars that are wider than long with both Rubrisciurus and Prosciurillus; the union of temporal ridges to form a sagittal crest anterior to the occiput with Rubrisciurus (but the temporal ridges are stronger, and the crest is longer in Rubrisciurus, forming one-third to three-fourths of the parietal length, depending upon age); and the position of the postorbital processes relative to the anterior margin of the braincase, and the relative size of the third molar with Prosciurillus. The combination of the other features in the diagnosis is unique to the Sulawesian ground squirrels.

Accounts of the two species of Hyosciurus are provided below. Qualitative morphological and quantitative morphometric comparisons between the two species are described and geographic and altitudinal distributions are outlined as derived from the collection localities of voucher specimens. The distinctiveness of the two species as defined by morphology and altitudinal distribution is supported by their sucking lice parasites. Each species of squirrel hosts a unique species of Hoplopleura (see the descriptions of sucking lice in the next section).

Gazetteer and Specimens Examined

Collection localities for the 53 specimens of H. heinrichi and the 14 examples of H. ileile studied are listed below. The number preceding each locality keys to a symbol on the map in figure 35.

Fig. 39

Specimen scores representing four population samples of Hyosciurus heinrichi (filled circle, Gunung Kanino, Gunung Nokilalaki, Pegunungan Latimojong and Pegunungan Takolekaju; N  =  32) and four population samples of Hyosciurus ileile (filled triangle, Gunung Ile-Ile, Sungai Tolewonu, Sungai Sadaunta, and Gunung Kanino; N  =  13) projected onto the first and second principal components extracted from principal-components analysis. Arrows identify scores representing holotypes of ileile and heinrichi. See table 47 for correlations and percent variance.

Fig. 40

Specimen scores representing four population samples of Hyosciurus heinrichi projected onto the first and second principal components extracted from principal-components analysis. Ellipses outline 95% confidence limits for scores of specimens from Gunung Nokilalaki (N, filled circle), Gunung Kanino (K, star), Pegunungan Latimojong (L, filled triangle), and Pegunungan Takolekaju (T, filled square). Arrow points to score for the holotype of heinrichi. See table 48 for correlations and percent variance.

Hyosciurus heinrichi

1. Gunung Kanino, 01°17′S, 120°08′E (estimated from Sheet SA 50-8), 4850 ft (1479 m): AMNH 225483, 225484.

2. Gunung Kanino, 5040 ft (1537 m), AMNH 225485; 5100 ft (1555 m), AMNH 225486.

3. Gunung Kanino, 5150 ft (1570 m): AMNH 225487.

4. Gunung Nokilalaki, 01°13′S, 120°08′E, 5700 ft (1738 m): AMNH 223541.

5. Gunung Nokilalaki, 5800 ft (1768 m): AMNH 223543, 223545, 225598.

6. Gunung Nokilalaki, 6500 ft (1982 m): AMNH 225465.

7. Gunung Nokilalaki, 6800 ft (2073 m): AMNH 225466, 225467; 6850 ft (2091 m), AMNH 225468.

8. Gunung Nokilalaki, 7000 ft (2134 m): AMNH 225469.

9. Gunung Nokilalaki, 7200 ft (2195 m): AMNH 225470.

10. Gunung Nokilalaki, 7300 ft (2226 m): AMNH 223542, 224544, 223548, 225471.

11. Gunung Nokilalaki, 7400 ft (2256 m): AMNH 225472, 225473; 7450 ft (2271 m), AMNH 223551.

12. Gunung Nokilalaki, 7500 ft (2287 m): AMNH 223546, 223547, 223549, 223550, 225474–82.

13. Pegunungan Takolekaju (“Molengraff Range,” the old European name for the mountain range, is notated on the specimen tags; no more precise collection locality is available; P. Jenkins, in litt., 2008), an extensive mountainous region in the western portion of the central core with the north-south boundaries between approximately 01° and 02°15′S, and extending slightly diagonally from about 119°45′E in the north to 120° near its southern ramparts, 4000–4300 ft (1220–1312 m): BMNH 40.641–40.652, 74.97.

14. Pegunungan Latimojong, 03°30′S, 121°23′E: 1600 m: AMNH 101311.

15. Pegunungan Latimojong, 2200 m: AMNH 101309; AMNH 101310 (holotype of Hyosciurus heinrichi), 196506.

We also examined BMNH 40.691b, 40.691c, and 40.691d from Tamalanti in Central Sulawesi, a place not indicated on the distribution map. Tamalanti, visited by the collector W.J.C. Frost in 1938, is a “Plantation between Rantekaroa [02°50′S, 119°50′E] and Koelawi [01°27′S,119°59′E]” (Laurie and Hill, 1954: 156), which was also the only information Musser and Paula Jenkins found when they searched through fieldnotes and other documents at BMNH. No elevation is notated on the specimen tags. Laurie and Hill (1954: 156) indicated that most of the animals collected by Frost at Tamalanti were recorded as coming from 3300–3800 ft (1006–1159 m), which seems too low for H. heinrichi.

Hyosciurus ileile

1. Gunung Ile-Ile, 00°58′N, 121°48′E (part of the larger Pegunungan Peleleh forming the mountainous backbone of the northwestern portion of the northern peninsula), 1700 m: AMNH 101308 (holotype of Hyosciurus heinrichi ileile), 196507.

2. Tolai, Sungai Tolewonu, 01°04′S, 120°27′E (estimated from Sheet SA 50-8), 550 ft (168 m): AMNH 226497.

3. Tolai, Sungai Tolewonu: 950 ft (290 m), AMNH 226498; 1100 ft (335 m), AMNH 226499.

4. Valley of Sungai Miu, Sungai Sadaunta (also spelled “Sidaonta” or Sidaunta”; tributary on right side of Sungai Miu), 01°23′S, 119°58′E (estimated from Sheet SA 50-8), 2900 ft (884 m): AMNH 224618.

5. Sungai Sadaunta, 3000 ft (915 m): AMNH 224619.

6. Sungai Sadaunta, 3150 ft (960 m): AMNH 224620.

7. Gunung Kanino, 01°17′S, 120°08′E (estimated from Sheet SA 50-8), 4600 ft (1402 m), AMNH 225459–62.

8. Gunung Kanino, 4800 ft (1463 m): AMNH 223540.

9. Gunung Kanino, 4960 ft (1512 m): AMNH 225463.

Hyosciurus heinrichi Archbold and Tate, 1935

Holotype and Type Locality

The holotype of Hyosciurus heinrichi is an adult male (AMNH 101310) collected by Gerd Heinrich on July 19, 1930. A stuffed museum study skin and accompanying skull comprise the holotype. The skin is intact as is the cranium and the mandible; all teeth are present (the skull, occlusal views of upper and lower cheek teeth, left dentary and right front foot are illustrated in Archbold and Tate, 1935: 3). Measurements are listed in table 42.

TABLE 42

Age, Sex, and External, Cranial and Dental Measurements (mm) for Holotypes of Hyosciurus ileile and Hyosciurus heinrichi

The type locality is Pegunungan Latimojong (“Latimojong Mts.”), 2300 m, in the northern section of the southwestern peninsula (see the maps and discussions in Heinrich [1932] and Stresemann [1940], and locality 15 in the gazetteer and map in figure 35), 03°30′S, 121°23′E, Propinsi Sulawesi Selatan, Indonesia.

Emended Diagnosis

A ground squirrel distinguished from species of endemic tree squirrels in Rubrisciurus and Prosciurillus by the traits enumerated in the generic diagnosis. Morphologically similar to Hyosciurus ileile but differs by having: (1) a much longer muzzle; (2) darker upperparts; (3) dark brownish gray underparts marked by a narrow midventral white swath with irregular borders that is broken up into white segments in some individuals; (4) slightly longer and thinner claws relative to size of feet; (5) larger ears but average shorter body, tail, and hind foot, as well as less mass; (6) much longer and slimmer rostrum; the tube formed by nasals and premaxillaries projecting farther beyond front faces of incisors; (7) longer nasals relative to length of frontals; (8) anterolateral rim of anterior opening of infraorbital canal slanted; (9) dorsal process of jugal lower, producing a more gracile zygomatic arch; (10) pterygoid fossae much narrower; (11) foramen ovale about twice as large; (12) posterior border of bony palate without a median projection in most specimens; (13) body of dentary slightly lower, posterior border between condyloid and angular processes more deeply concave. Hyosciurus heinrichi also differs from H. ileile in absolute means and proportions of the cranial and dental dimensions described in the section covering comparisons.

Geographic and Altitudinal Distributions

The latitudinal and longitudinal boundaries of H. heinrichi on Sulawesi are unknown, but the species may occur only in the mountainous west-central core of the island if the collection localities of voucher specimens reflect its real distribution (see gazetteer and map in figure 35). Samples come from the northern area (Gunung Kanino and Gunung Nokilalaki), the central region (Pegunungan Takolekaju and Tamalanti), and the southern highlands (Pegunungan Latimojong) of the western mountain block. The distribution of H. heinrichi in this western mountainous region of Sulawesi's central core is concordant with a suite of mammals—three species of shrews, at least two and possibly three tarsiers, a tree squirrel, and 14 species of murid rodents—that are so far known only from forest habitats in this region (table 25).

Elevational collection records that we judge to be reliable range from 1479 m in lower montane rain forest to 2287 in upper montane rain forest. This bracket contains elevations recorded by Musser on Gunung Kanino and Gunung Nokilalaki, and those made by Heinrich on Pegunungan Latimojong. W.J.C. Frost took specimens between 4000 and 4300 ft (1220–1312 m) on Pegunungan Takolekaju (Molengraff range), which is probably at the lower limit of lower montane rain forest. The three specimens collected by Frost from Tamalanti have no elevations recorded on the skin labels. Laurie and Hill (1954: 156) claimed that most of Frost's material from Tamalanti was obtained between 3300 and 3800 ft (1006–1159 m), but this range is within tropical lowland evergreen rain forest and too low for H. heinrichi, judged from Musser's experience with the species along his transect.

Description

Hyosciurus heinrichi is a moderately large, long-nosed, dark brown, and short-tailed ground squirrel (length of head and body, 195–240 mm; length of hind foot, 51–61 mm; weight, 228–370 g; extremes from table 43). Among the species of squirrels endemic to Sulawesi, H. heinrichi is slighter smaller than H. ileile and Rubrisciurus rubriventer in physical size but much larger than members of the Prosciurillus leucomus and P. murinus groups (table 3).

TABLE 43

Descriptive Statistics for Measurements (mm) of Lengths of Head and Body, Tail, Hind Foot, and Ear, and for Weight (g) Derived from Samples of Hyosciurus heinrichi and Hyosciurus ileile^a Mean ± 1 SD, observed range (in parentheses), and size of sample are listed. Mean values were used to compute LT/LHB. Specimens measured are listed below.^b

Chocolate brown fur flecked with buff and black covers the upperparts from the head to the base of the tail, including the ears, which lack tufts. The mix of dark gray wooly underhairs tipped with pale buff, longer overhairs that are dark gray or blackish along most of their lengths with a subterminal ochraceous or pale buffy band and black tip, and glistening black guard hairs combine to produce the lustrous dark brown cast to the pelage, which is also soft and dense (15–18 mm thick over the back). On the top of the neck just behind the ears the fur is reversed and then parted along the midline exposing the skin along a 30–40 mm strip. Each eye is surrounded by a hairless dark buffy ring. Dorsal surfaces of the front and hind feet are black to blackish gray, the palmar and plantar surfaces are black. Claws on the front digits are long, slim, and only slightly recurved (see the illustration in Archbold and Tate, 1935), 30%–35% of the length of the front foot (15%–20% for the much shorter and deeply recurved claws of the species of Rubrisciurus and Prosciurillus), and almost as long as the digits. Claws on digits of the hind feet are also slim and gently arcuate but are shorter (12%) relative to length of the foot.

Fur covering the underparts is white and dark grizzled brown in various patterns. Among the specimens from Gunung Kanino, Gunung Nokilalaki, Pegunungan Takolekaju, and Pegunungan Latimojong, the fullest expression is exhibited by five specimens: a pure white strip with ragged margins extends from the chin to the base of the tail and down inside each thigh (hairs are unpigmented for their entire lengths; the strip may appear cream on dry skins but is white on freshly caught squirrels). This midventral white swath is bordered by dark brownish gray ventral fur speckled with pale buff (hairs are very dark gray for most of their lengths and tipped with buff). The ventral region in the remainder of the sample of H. heinrichi can be sorted into five categories that roughly illustrate the nature of variation in venter pattern. (1) A white midventral strip extends from chin to groin, has uneven margins, and is broken up by a small dark brown midventral spot on the lower abdomen. (2) A white strip is interrupted by an elongate midventral dark brown patch on lower abdomen, and the grizzled brown of the abdominal margins protrudes into the white strip as round blobs on the upper abdomen and chest. (3) The white portion is reduced to a solid strip from the chin to upper abdomen where it splits into two white threads that bound a large midventral grizzled brown area, then rejoin to form a solid white expanse at the base of the tail. (4) The entire underparts are dark grizzled brown with a patch of white covering the chin, neck and chest, and another covering the inguinal region—the two white areas are separated by a expanse of grizzled brown; some specimens show a diffuse, wispy thread of white, interrupted in places, extending between the two solid white areas, and usually present only on one side. (5) Solid white covers the chin, throat, and chest, grizzled brown overlays the upper abdomen, and white covers the lower abdomen and inguinal region; the two solid white regions are wispily connected by a few white hairs along the midventral line through the brown area. From a solid white midventral strip (wide but not extending to lateral margins of the underparts) with uneven margins, the range of variation reflects a fracturing of that strip into white and brown areas by incursions to different degrees of the dark brown lateral margins of the venter fur.

Slightly less than half the length of head and body (LT/LHB  =  45%–47%), the tail is very dark brown with buffy and black highlights, coloration similar to the upperparts of the head and body.

Females have three pairs of teats: one abdominal pair (situated in the middle of the abdomen) and two inguinal pairs. The number matches that in all the species of Prosciurillus, but the most anterior pair is postaxillary in position in Prosciurillus, not in the middle of the abdomen. One or two young comprise a litter. No embryos were found in the few mature females examined, but one specimen had a placental scar in one uterine horn, and two squirrels had one scar in each horn.

Views of the elongate skull are illustrated in figure 36. Note the protracted rostrum and its prominent projection beyond the incisors, the moderately strong temporal ridges meeting to form a short sagittal crest, the short orbit, relatively low jugal component of the zygoma, postorbital process even with anterior surface of the braincase, position of the posterior margin of the bony palate relative to backs of the parallel tooth rows, very narrow ptergoid fossae bounded by a slight lateral ridge, spaceous foramen ovale, posterior maxillary foramen at each posterolateral margin of the bony palate, incisors emerging from the rostrum at a right angle (orthodont configuration), relatively smaller third upper molar, and slender but sturdy dentary. Cranial and dental measurements are summarized in table 44.

Fig. 41

Habitat of Hyosciurus heinrichi in upper montane rain forest on Gunung Nokilalaki, 2256 m. The tree squirrels Prosciurillus topapuensis and P. murinus also live here. The range of ambient temperatures recorded during the sampling period is listed in table 2. Photographed in 1975.

TABLE 44

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Population Samples of Hyosciurus heinrichi Mean ± 1 SD and observed range (in parentheses) are listed.

Comparisons

Hyosciurus heinrichi needs to be compared with the only other species in the genus, H. ileile. Both species share a similar physical build, but H. heinrichi is more gracile and less stocky than H. ileile, with a much longer muzzle. Typically, H. heinrichi has larger ears; a shorter body, tail, and hind foot; and weighs less (table 43).

The external dimensional contrasts are multivariately summarized in the ordination of scores projected onto the first and second principal components extracted from principal-components analysis illustrated in figure 38. The points form two clusters that barely overlap along the second axis but do so to a greater extent along the first component. The very high positive score for length of tail along with the lower and positive scores for length of head and body, and length of hind foot, contribute to the distribution of scores along the first axis (table 46), pushing the bulk of the scores representing specimens of H. ileile to the right of the H. heinrichi constellation, a reflection of the average greater lengths of these dimensions shown by H. ileile (table 43). Length of ear loads heaviest along the second component followed by length of head and body, and then length of hind foot. Clearly reflected here are the relatively much larger ears of H. heinrichi compared with H. ileile, and its relatively shorter body and hind feet.

Differences also exist between the two species in pelage coloration. Fur covering upperparts of head and body is dark brown flecked with buff and black in both species, but the coat of H. heinrichi is thicker, 15–18 mm as opposed to 10–12 mm in H. ileile, and appears slightly darker due to the longer, darker hairs. Fur on the neck just behind the ears is reversed followed by a part in both species, but the median part is 30–40 mm long in H. heinrichi and only 10 mm long in H. ileile. Coloration of the front and hind feet are similar in the two species although the palmar and plantar surfaces of H. heinrichi tend to be darker, black rather than slate gray as in H. ileile.

Color pattern of the ventral fur differs. It is dark grayish black speckled with pale buff on Hyosciurus heinrichi and marked by a midventral pure white region with irregular borders that is variable in coverage of the underparts. In its fullest extent, the white swath is moderately wide, but never covers the entire width of the underparts, and reaches from the chin to the base of the tail and inner surfaces of the thighs. Its weakest expression is a pattern where dark brown ventral fur covers the upper abdomen separating a white swath on the chin, throat, and chest from the white covering the lower abdomen and inguinal region (a detailed exposition of the range is provided in the section on description).

The entire venter, from the chin to base of the tail and inner surfaces of the thighs is cream-colored in H. ileile, not pure white as in H. heinrichi (Musser recorded this chromatic distinction in the field as seen on freshly caught animals). The cream swath covers nearly the entire venter and is bounded by even borders. On each specimen from the central core of Sulawesi and the two from Gunung Ile-Ile, the cream underparts are interrupted by a small midventral brown area. At one end of the variation of spotting in the samples from Musser's transect is a specimen that displays a small (5 × 10 mm) midventral spot between the thighs. At the other end is a squirrel with a thin midventral brown strip reaching from the abdomen to base of the tail. Of the rest of the specimens, one has two midventral brown spots on the lower abdomen, and the rest show a single brown blob (10 × 20 mm) in the middle of the lower abdomen. Among the two squirrels from Gunung Ile-Ile, the holotype has a narrow patch of midventral brown hairs on the lower abdomen (not obvious because the patch was sewn into the seam after the skin was stuffed), and a round brown incursion in the right postaxillary region. Lateral borders of the cream portion are uneven because of the uneven way the skin was sewn. The other specimen has a tuft of brown hairs in the inguinal region (partially concealed in the sewn seam). The range in patterning of the venter that is seen in H. heinrichi is not present in H. ileile.

Both species have long claws but those of H. heinrichi are slightly slimmer (more gracile) and longer relative to length of foot (30%–35% of front foot length in H. heinrichi, 25%–28% in H. ileile).

The majority of differences between the two species expressed in the skull reflect in H. heinrichi a greater specialization associated with the elongated rostrum and a less specialized conformation in H. ileile. The protracted muzzle of H. heinrichi compared to the shorter version typical of H. ileile extends to the cranial architecture (figs. 36, 37). Mean values of dimensions from the back of the skull—its breadth (indexed by MB), postpalatal region (PPL), breadth of the bony palate (BBP), and length of the tooth row (CLPMM)—are not significantly different in the two species (tables 44, 45). On the other hand, the mean values of dimensions describing the facial skeleton—lengths of the rostrum (LR), nasals (LN), diastema (LD), bony palate (LBP), and projection of the bony nasal tube beyond the upper incisors (LPT)—are much greater in H. heinrichi than in the sample of H. ileile, and the rostrum is not as deep (HR), reflecting the absolutely longer, slimmer, and more protracted rostrum of H. heinrichi, and its much longer extension beyond front faces of the incisors compared with the shorter and broader anterior half of the skull in H. ileile. Paralleling the longer rostrum of H. heinrichi is its longer skull (ONL, CBL). The skull of H. heinrichi is also typically narrower (narrower zygomatic breadth, ZB), with a narrower interorbital region (IB), shorter orbit (LO), shallower braincase (HBC), and much smaller ectotympanic bullae (LB) compared with those dimensions in H. ileile.

Fig. 42

Habitat of Hyosciurus heinrichi in upper montane forest on Gunung Nokilalaki, 2256 m. Traps set on top and beneath the rotting log in foreground took examples of H. heinrichi, which is common on the summit and upper slopes in this mossy, wet and cold forest. Photographed in 1975.

TABLE 45

Descriptive Statistics for Cranial and Dental Measurements (mm) Derived from Population Samples of Hyosciurus ileile Mean ± 1 SD and observed range (in parentheses) are listed.

TABLE 46

Results of Principal-Components Analysis Contrasting Population Samples of Hyosciurus ileile with Those of Hyosciurus heinrichi from Central Sulawesi Principal components are extracted from a covariance matrix of log-transformed values for lengths of head and body, tail, hind foot, and ear; see figure 38.

Qualitative contrasts involving the nasals, jugal, opening of the infraorbital foramina, bony palate, pterygoid fossa, foramen ovale, and dentaries also distinguish the two species. Nasals of H. heinrichi are about as long as the frontals, those of H. ileile are shorter than the frontals (83%–86% the length of the frontals). The jugal of H. heinrichi is low and the entire arch is gracile, while the jugal of H. ileile has a higher dorsal process and the arch appears more robust (not shown in the drawings as clearly as is seen on specimens). We did not measure jugal height but the contrast between the two species is evident when skulls are compared side-by-side. The lateral lip of the infraorbital canal is typically at a slant in H. heinrichi but vertical in H. ileile. Most specimens of H. heinrichi are without a conspicuous midventral posterior projection on the posterior margin of the bony palate (fig. 36); a very few display a midventral nubbin on the bony margin or a slightly larger bump. All the examples of H. ileile except the specimen portrayed in figure 37 have a prominent midventral process at the posterior margin of the bony palate. The pterygoid fossa in H. heinrichi is narrow, its lateral margin defined by an inconspicuous low ridge. Hyosciurus ileile has a much wider fossa, its surface triangular from ventral perspective, and marked laterally by a higher ridge; the shape, relative surface area of the fossa, and height of the bordering ridge form a configuration closely similar to that seen in the species of Prosciurillus (figs. 12–Fig. 1314). Each foramen ovale is spacious in H. heinrichi, about twice the size of comparable foramina in H. ileile. Finally, H. heinrichi has a slightly slimmer dentary as indicated by its lower ramus, and the posterior border between condyloid and angular processes is more deeply concave than the configuration in H. ileile with its somewhat deeper ramus and shallower posterior border.

Two widely spaced clusters contained in the ordination of specimen scores projected onto the first and second principal components extracted from principal components analysis in figure 38 mirror the cranial differences described above. The position of the H. ileile cluster to the left and the H. heinrichi group to the right along the first axis is influenced mostly by the high and positive loadings for lengths of nasals, rostrum, and diastema along with extent of the rostral projection beyond the incisors (table 47); the moderate but still positive loadings for lengths of skull and bony palate; and the moderate to high negative values for interorbital breadth, heights of rostrum and braincase, and lengths of orbit and bulla. Loadings for breadths of the braincase (mastoid breadth) and bony palate as well as lengths of the postpalatal region and tooth rows have a marginal effect on producing the two clusters along the first principal component. The pattern of scores in this principal-components ordination is a multivariate analytical summary of the cranial differences between the two species of Hyosciurus that is also expressed by mean values of cranial dimensions (tables 44, 45) and can be seen in the illustrations of skulls (figs. 36, 37): H. heinrichi has an appreciably longer and more slender rostrum, narrower interorbital region, shorter orbit, shallower braincase, and smaller ectotympanic bullae compared with the cranial dimensions in H. ileile; skulls of H. heinrichi appear gracile, thin, and long, those of H. ileile appear stocky and short by comparison.

Fig. 43

An adult male Hyosciurus ileile caught at 155 m above camp on the Sungai Tolewonu in tropical lowland evergreen rain forest. The squirrel was trapped on a large decaying trunk (2 ft in diameter) forming a bridge 15 m long straddling the river, one end on a narrow bank at base of steep hillside, the other resting on river terrace 3 ft above the water surface; caught about 10:30 a.m. See account of this species for description of behavior and diet. See table 2 for range of ambient temperatures recorded during the trapping duration at the Sungai Tolewonu. Photographed in 1976.

TABLE 47

Results of Principal-Components Analysis Contrasting Population Samples of Hyosciurus ileile with Those of Hyosciurus heinrichi Principal components are extracted from a covariance matrix of log-transformed values for 18 cranial and 1 dental variable; see figure 39.

The bony mandibular architecture is similar in the two species (figs. 36, 37). The dentaries of each species are about the same length, but the body of the ramus is not as deep in H. heinrichi as it is in H. ileile, a distinction shown in the figures of skulls (we did not measure the mandibles).

Among the traits Tate and Archbold (1936: 1) used to separate H. ileile from H. heinrichi was the smaller third premolar (“a mere spicule”) and first molar of H. ileile and its narrower pterygoid fossa ( =  mesopterygoid fossa). Of the two specimens in the type series from Gunung Ile-Ile, the holotype (AMNH 101308) has small, thin, and peg-like third premolars, and the other (AMNH 196507) has a small right third premolar, but lacks the left third premolar. Small to robust third premolars describes the range of variation in the series of H. ileile from the central core of Sulawesi, and a similar range in size occurs in our large sample of H. heinrichi. We detected no appreciable difference between the two species in size of the first molar or breadth of the mesopterygoid region; Corbet and Hill (1992) also did not appreciate the differences noted by Tate and Archbold.

Geographic Variation

Judged by head-and-body length, the specimens of H. heinrichi from Pegunungan Takolekaju average slightly larger than the series from Pegunungan Latimojong, Gunung Kanino, and Gunung Nokilalaki; however, absolute length of tail and tail length relative to body length, along with length of hind foot, are closely similar among all four geographic samples (table 43).

Color of the fur is comparable among the samples. All contain squirrels with chocolate brown upperparts and blackish feet. Underparts are white and blackish gray configured into a range of patterns as we described previously.

Mean values of cranial and dental dimensions reveal a picture of geographic variation that is summarized by the descriptive statistics listed in table 44 and results of multivariate analyses presented as specimen scores projected onto the first and second principal components extracted from principal-components analysis (fig. 39). Covariation in most variables influenced the spread of scores along the first axis (table 48), which reflects the greater size of certain dimensions in the sample from Pegunungan Takolekaju compared to the samples from Pegunungan Latimojong and from Musser's transect along Gunung Kanino and adjacent Gunung Nokilalaki. Mean values for some of the variables—length of skull and tooth row, breadth of the interorbital region, height of rostrum, and breadth of the bony palate—exceed those in the sample from Gunung Kanino and Gunung Nokilalaki (table 44).Fig. 40

Fig. 44

A closer look at the squirrel shown in figure 43, just as it was fleeing the confines of the cage.

Fig. 45

Specimen scores representing four population samples of Hyosciurus ileile projected onto the first and second principal components extracted from principal-components analysis. Symbols identify scores for specimens from Gunung Ile-Ile (filled circle), Sungai Tolewonu (star), Sungai Sadaunta (filled square), and Gunung Kanino (filled triangle). Arrow identifies score for the holotype of ileile. See table 50 for correlations and percent variance.

TABLE 48

Results of Principal-Components Analysis Contrasting Population Samples of Hyosciurus heinrichi Principal components are extracted from a covariance matrix of log-transformed values for 18 cranial and 1 dental variable; see figure 40.

Scores representing the four specimens from Pegunungan Latimojong fall between those from Musser's transect and the series from Pegunungan Takolekaju. The ellipses that outline 95% confidence limits for scores of specimens in each geographic sample indicate the relative homogeneity of the samples from Gunung Kanino and Gunung Nokilalaki (the former is a high ridge attached to the latter and unbroken montane forests cover both highlands), the separation of the Takolekaju sample from the Kanino-Nokilalaki specimens, and the intermediate position of the Latimojong series. This is somewhat surprising because Pegunungan Takolekaju lies between the highlands along Musser's transect and Pegunungan Latimojong, which is at the southern end of the mountains forming the western part of Sulawesi's central core (see map in fig. 35). Our analysis reveals variation in certain cranial dimensions among the three basic geographic samples—Gunung Kanino + Gunung Nokilalaki, Pegunungan Latimojong, and Pegunungan Takolekaju—with those from Musser's transect exhibiting the smaller skulls and those from Pegunungan Takolekaju the largest. What is the significance of these results? Does the variation in cranial and dental measurements among present samples simply reflect geographic variation due to differing intensities of gene flow among populations, or point to the Takolekaju sample as representing a population genetically isolated—or nearly so—from the other montane populations of ground squirrels? We do not know. Within a wide-ranging montane species like H. heinrichi, we would expect some morphometric variation from place to place, especially among highlands supporting montane forest habitats that are separated by major river valleys or lowland evergreen rain-forest habitats. Uncovering existing patterns of genetic continuity or partial interruption among populations of H. heinrichi will depend on analyzing variation in external, cranial, and dental measurements among larger samples from more locations in the western mountain block south of Musser's transect. Compared with the large series from Gunung Kanino and Gunung Nokilalaki, there are only a few specimens in each of the samples from Pegunungan Takolekaju and Pegunungan Latimojong, and there are no specimens from montane regions between any of present collection sites. Fewer specimens per collection site would be required for extracting DNA samples, but broad geographic coverage would still be required.

In addition to the four geographic samples discussed above, a fifth, Tamalanti (see gazetteer), is closer to Gunung Kanino and Gunung Nokilalaki than to the other two collection sites; yielded three specimens that we did not measure because the skulls were incomplete or their condition otherwise unsatisfactory. During one visit to the British Museum, Musser compared the three skulls with his material and found them to be inseparable in overall size.

Ecology

Hyosciurus heinrichi is terrestrial, diurnal, and inhabits cool and damp montane forests along streams, on hillsides, and on ridgetops (see table 2 where ambient temperature regimes are listed for Gunung Nokilalaki and Gunung Kanino). Musser worked only in primary forest on those highlands, so we do not know if populations of this ground squirrel can successfully inhabit second-growth forest or scrub habitats. On Gunung Nokilalaki, Musser caught the squirrels with Conibear traps placed in wide and prominent runways along the side of cut banks on steep slopes and along rock faces; beneath rotting, moss-covered tree trunks; under wet, mossy tangled trunks and limbs of rotting tree-falls; and among the mossy roots of rotting stumps and living trees (figs. 41, 42). Some of the runways ended in freshly dug burrows. In the vicinity of Gunung Kanino, Musser trapped the squirrels on tree trunks and limbs lying across the Sungai Tokararu (see trapping summary in table 49).

Fig. 46

Hoplopleura rubrisciuri, male. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Fig. 47

Hoplopleura rubrisciuri, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

TABLE 49

Summary of Habitat at Trapping Sites, Stomach Contents, and Other Relevant Information for Specimens of Hyosciurus heinrichi Collected by Musser in Central Sulawesi, 1973–1975 Collection locality, specimen number, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). Collection localities on Gunung Kanino are in lower montane rain forest, those on Gunung Nokilalaki are in upper montane rain forest. All squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

The furtive and quiet H. heinrichi, although common, is rarely seen in its dark and wet mossy forest habitat. Musser was fortunate to observe three individuals on the summit of Gunung Nokilalaki at 10:00 a.m. on a sunny day in April for about half an hour. At that spot the understory was open with scanty ground cover compared to the denser forest downslope where the thick understory made it nearly impossible to see the ground squirrels. Each of the squirrels was in the open, each had dashed from a runway, stopped in the clearing on a rock or raised point of ground, then dashed off again to disappear along or beneath a rotting tree trunk or stump and reappear again in the general vicinity. When running they appeared as long blackish streaks. At times each would stop, sit on its haunches, and twitch its tail much as all ground squirrels do, but never vocalize, then streak off and eventually disappear from sight. This was an exceptional encounter because squirrels were sometimes heard rustling through the undergrowth, but rarely seen.

A year later, on another April morning, Musser watched an individual for 10–15 minutes in a different area of forest on the summit of Nokilalaki. He stood about 10 ft from the squirrel, which was sitting on a rotting tree trunk covered with thick moss. From a distance, the squirrel resembled a round, dark brown ball of fur with a long face and big eyes. At first it responded to Musser's presence by leaping to the ground and scampering away for a few feet, but then returned to the top of the trunk to sit, occasionally grooming and biting ectoparasite-infested areas, scratching at other places in its fur, and sometimes chirping and sniffing about on the tree trunk. The squirrel kept its tail pressed closely to its back while sitting, jerking it along the back with every chirp. When the squirrel emitted a long series of calls, its tail would extend out behind the body; afterword, the tail reverted to its position against the squirrel's back. Often the squirrel would jump to the ground, scamper beneath the trunk where it remained for a minute or so looking over several old acorn husks, groom itself, and vocalize again. Once, after emitting a series of chirps it slowly approached Musser with nervous, jerky movements, stopping within 3 ft of him, and twitching its tail up and down before quickly scampering back to the trunk. Finally, Musser moved closer to the trunk, and the squirrel streaked away over the wet ground chirping continuously as it went, holding its tail straight behind its body.

The squirrel's voice was distinct from that of any species of the tree squirrels Prosciurillus and Rubriventer that Musser heard vocalize. As it sat, the ground squirrel uttered a string of single chirps, sounding more like a bird and not at all like a squirrel. When the squirrel became nervous or frightened, the calls increased in frequency and and the chirps had the slight suggestion of a chuck. Once or twice it became very agitated and chattered as most squirrels do, but the sounds were still soft, without the timber or resonance of the tree squirrels. Its bird-like vocalizations were deceptive, and as Musser worked daily in the forest, he did not know if the chirps heard most of the mornings issued from ground squirrels or birds.

Judged from contents of stomachs, the diet of Hyosciurus heinrichi consists of arthropods and some fruits, primarily acorns (fruit from species of Lithocarpus); see summary of stomach samples in tables 49 and 57. Some stomachs contained only arthropods, others arthropods and acorn mash, and a few were filled only with acorn mash. Geophilomorph and Scolopendromorph centipedes, the occasional ponerine and formicine ants and ant pupae, long-legged cursorial beetle larvae, several other kinds of beetle larvae with short legs, adult beetles, cockroaches, and certain kinds of fly larvae (Diptera) comprise an arthropod suite common to leaf litter (D. Grimaldi, personal commun., 2009). Another group of dipteran larvae found in stomachs, the Sciaroidea, live just below the ground surface and in wet moss; the female fly oviposits in the wet ground or moss below the surface and the eggs hatch into a ball of larvae. With its elongate muzzle and very long claws, the ground squirrel locates prey, then scratches and pokes through the leaf pack and moss (small segments of moss were found in stomachs) to pounce on any arthropods encountered. Exposing the subsurface soil environment with its long claws would allow the squirrel access to the larval Sciaroidea dipterans. In stomachs, this suite of leaf litter and subsurface arthropods were often contained in a clay-like ball separate from acorn mash. No stomach examined contained the large beetle larvae, usually legless, that live in rotting wood; such kinds of larvae were found in many stomachs of Rubrisciurus rubriventer.

The cranial architecture common to specimens of H. heinrichi exhibits adaptations well suited for procuring the dietary components found in contents of stomachs. A very long nasal region likely contains increased nasal epithelium that would enhance olfactory acuity. To a human, odors from wet soil, decaying leaf litter and rotting treefalls, and soaked moss saturate the air in mossy forest, and must be even more concentrated to a squirrel, which has better olfactory ability. Detecting dipteran larvae in wet ground and moss, and other arthropods within soaked and compressed leaf litter on the surface, probably requires heightened olfactory acuity that would cut through the prevailing ambient forest odors.

Opening acorns, a tough woody fruit, requires strong incisors along with forceful contributions from masseter and temporal muscles, and high premolars and molars affording surfaces for the mechanical breakdown of nuts over the squirrels' lifetime. Prominent temporal ridges meet in the midline near the occiput to form a short sagittal crest on the skull of H. heinrichi, the jugal component of each zygomatic arch is high, and the dentary elongate but robust; all provide firm origins and insertions for the array of masticatory muscles. This myological complex is joined by narrow but strong incisors, and large, high cheek teeth (fig. 36). Except for a shorter rostrum, the architecture is basically similar in H. ileile (fig. 37). The morphology contrasts sharply with that peculiar to the Indomalayan shrew-faced squirrel, Rhinosciurus laticaudatus, which has weak incisors that are very reduced in size relative to bulk of the skull, low cheek teeth that quickly wear to occlusal basins, slight temporal ridging extending to the occiput without forming a sagittal crest, low jugal, and delicate dentary (see illustration of skull in Corbet and Hill, 1992). Only arthropods and earthworms are eaten by this tropical ground squirrel (Davis, 1962; Medway, 1969; Payne et al., 1985), and that diet is reflected in the structure of its teeth and skull.

The small-bodied terrestrial shrew rat Melasmothrix naso occupies the same wet, mossy montane forest habitat as Hyosciurus heinrichi. With its long muzzle and claws, dark chestnut fur, short tail, and diurnal activity, the murid resembles a small version of the ground squirrel. Melasmothrix naso digs into the wet moss and ground for Sciaroidea dipteran larvae, but also eats earthworms (Musser, 1982). No annelids were found in stomachs of the ground squirrel.

Stashes of empty acorn hulls are scattered through the montane forest beneath tree roots, rotting tree trunks lying on the ground, and tree holes just above ground. Many of the piles probably resulted from ground squirrel activities. Most of the empty hulls were in halves, some were mostly intact except for a small hole large enough to allow extraction of the seed. The ripe seed consists of a firm, white or gray endosperm enclosed by a thin brown seed coat. The squirrels eat the entire seed and it shows up in stomach samples as a semi-dry granular whitish or pale grayish mass (the endosperm) riddled with brown flecks (the seed coat).

Lithocarpus havilandii is the common oak in the mossy forest on Gunung Nokilalaki where older trees contribute to the canopy and younger trees and saplings are scattered throughout the understory. During December of 1973, acorns rained from the trees and littered the ground where they became forage for native pigs (Sus celebensis) and rodents. At lower altitudes in lower montane forest on Gunung Kanino, L. glutinosus and L. elegans replace the upper montane L. havilandii. In some places they are scattered through the forest on hillsides and ridgetops; in other areas they form large groves.

The fruit segment of the diet described here for H. heinrichi represents records for only part of a year. What fruits the squirrels may eat during other months, during the short dry season on the mountain, and at times when acorn production is unusually low, is unknown. Judged from stomach samples (table 49), fruit from oaks is preferred, but some unidentifiable fruit remains were present in a few stomachs. Fruit of chestnuts, Castanopsis acuminatissima, for example, may also be eaten. Groves of chestnuts intermingled with oaks and Calophylum are common on the upper slopes of Gunung Kanino and lower reaches of Gunung Nokilalaki to about 1800 m. Musser's observations contribute a degree of ecological information for H. heinrichi, but there is much more to learn about the ecology of this squirrel.

Ectoparasites

The sucking louse Hoplopleura heinrichi, n. sp. (see description in following section), uniquely parasitizes Hyosciurus heinrichi. The only other ectoparasite records consist of immature (larvae and/or nymphs) stages of hard ticks (Acari, Ixodoidea) belonging to the genera Amblyomma and Haemaphysalis (Durden et al., 2008; also see table 56 and ectoparasite account for Rubrisciurus rubriventer).

Sympatry

The range of H. heinrichi on the central core of mainland Sulawesi overlaps those of Prosciurillus topapuensis, P. murinus, and Rubrisciurus rubriventer (table 6). Along his transect in the northern portion of central Sulawesi, Musser trapped H. heinrichi in the same traplines that yielded the species of Prosciurillus and Rubrisciurus, and sometimes in the same traps (table 49).

Voucher specimens from collection sites along Musser's transect around Gunung Kanino indicate that in Sulawesi's central core Hyosciurus heinrichi and H. ileile are regionally sympatric but locally parapatric in an elevational pattern where the lower border of the range of the montane species abuts the upper margin of the range for the lowland species. Musser never encountered the two species in the same trapline. The spatial relationship is roughly portrayed on the inset map showing the distribution of collection sites for each species (see fig. 35). From the southwestern side of Gunung Nokilalaki extends a high ridge that is bisected in the middle by a stream, the Sungai Tokararu (labeled on the map in fig. 4); the local people refer to the ridge on the west of the stream as Gunung Tokararu and that to the east as Gunung Kanino (both ridges are labeled on the inset map in fig. 35). The Tokararu originates below the summit of Nokilalaki, flows into a deep ravine along the northwestern margin of Gunung Kanino to pass through the cleft between the two ridges, and eventually empties into the waters of Danau Lindu. Musser worked on the top and upper sides of the Kanino ridge, on up to the summit of Nokilalaki on the eastern side of the Sungai Tokararu, and along the Tokararu stream at lower altitudes where it flowed alongside the Kanino ridge.

He collected H. heinrichi from the summit of Nokilalaki downslope east of the Tokararu to 1738 m, and along the Sungai Tokararu at the northwestern base of the Kanino ridge from 1570 m down to 1479 m (see gazetteer). He encountered H. ileile on the southeastern slope of the Kanino ridge just below the ridge-top and on the northwestern side just below the top of the ridge in a ravine containing the Sungai Salubeka, which is a small tributary of the Sungai Tokararu (and is drawn on the inset map in fig. 35 between localities 7 and 8, and labeled on the map in fig. 4); squirrels were trapped at 1512, m, 1463 m, and 1402 m, and encountered again along the Sungai Sadaunta below Danau Lindu between 884 m and 960 m.

In the Kanino area, the range of each species appears to reflect a parapatric pattern. Hyosciurus heinrichi was caught in the stream valley of the Tokararu at the base of the Kanino ridge and H. ileile was taken on the ridge itself just below the top (see tables 49 and 51 for habitats at each collection site). Parapatry may describe the ranges of the two species throughout the western mountains of the central core but no data are currently available to test this speculation. Both are similar in physical size, and both consume fruit, primarily acorns, and arthropods (see tables 43, 49, 51, and 57) and it seems unlikely that they would be found together at the same site. While samples of H. heinrichi have been obtained in the mountains south of Musser's transect (see gazetteer and fig. 35), no examples of H. ileile have ever been collected there, which may indicate its true absence but is more likely an artifact of trapping effort. Musser found H. heinrichi to be common in montane habitats and H. ileile to be uncommon wherever it occurred; short trapping periods (a few days) would produce the former but longer durations (months) and targeted trapping days would be required to sample the latter.

Synonyms

None.

Hyosciurus ileile Tate and Archbold, 1936

Hyosciurus heinrichi ileile Tate and Archbold, 1936: 1.

Holotype and Type Locality

The holotype of Hyosciurus ileile is a young adult female (AMNH 101308) collected by Gerd Heinrich (collector number 130) on November 21, 1930. A stuffed museum study skin and accompanying skull comprise the holotype. The skin is intact, as is the cranium with mandibles; all teeth are present. Measurements are listed in table 42.

The type locality is Gunung Ile-Ile, 00°58′N, 121°48′E (part of the larger Pegunungan Peleleh forming the mountainous backbone of the northwestern portion of the northern peninsula), 1700 m (see the maps and discussions in Heinrich [1932] and Stresemann [1940], and locality 1 in the gazetteer and map in figure 35), the extreme northwestern part of Propinsi Sulawesi Tengah, Indonesia.

Emended Diagnosis

Hyosciurus ileile is most similar to H. heinrichi in morphological attributes, but differs in (1) its somewhat brighter upperparts; (2) typically mostly solid cream underparts; (3) shorter and blunter muzzle; (4) smaller ears; (5) heavier body and longer hind feet; (6) slightly shorter claws relative to size of feet; (7) shorter and more robust rostrum; (8) shorter projection beyond incisor faces, and shorter nasals that are not as long as the frontals; (9) higher jugal that forms a more sturdy zygomatic arch; (10) higher and wider skull on average; and (11) different cranial proportions, as described in the account of H. heinrichi (see section detailing comparisons).

Geographic and Altitudinal Distributions

The actual distribution of Hyosciurus ileile on Sulawesi is unknown. The few localities from which voucher specimens have been obtained include one montane area in the northwestern portion of the northern peninsula (Gunung Ile-Ile) and several places in the northern portion of the island's central core in tropical lowland evergreen and lower montane habitats (see gazetteer and map in figure 35). The species certainly has a broader distribution than present samples indicate, and should be sought elsewhere in the central core of the island, and on both the east-central and southeastern peninsulae. Its range on the northern peninsula most likely extends beyond Gunung Ile-Ile; we would expect to find the squirrel in landscapes throughout the western curve of the peninsula, from the Gorontalo region west to the base of the peninsula.

The range of H. ileile may not extend from Gorontalo east to the northeastern tip of the peninsula. This region was transformed into one or more islands during warm periods in the Pleistocene when sea level was considerably higher than at present (Fooden, 1969; Bintanja et al., 2005). Two species of macaques (M. nigra and M. nigrescens) and four murid species (Echiothrix leucura, Taeromys taerae, Bunomys fratrorum, and Rattus xanthurus) occur east of Gorontalo and have never been recorded from the northern peninsula west of the Gorontalo area (Fooden, 1969; Groves, 2005; Musser, ms). All these mammals have close phylogenetic relatives elsewhere on Sulawesi and their phenetic and genetic distinctiveness likely evolved from ancestral populations that were isolated on the northeastern Pleistocene islands. After Archipelago Sulawesi was transformed into its present-day configuration, some mammal species formerly occurring only in the western section of the northern peninsula and central part of the island may have gradually occupied habitats east of Gorontalo. Two species of murid rodents provide examples. Bunomys chyrsocomus now occurs in forests throughout most of Sulawesi, including the northern peninsula where it is sympatric with Bunomys fratrorum in the region west of Gorontalo. Rattus marmosurus, a member of the Rattus xanthurus group (Musser and Carleton, 2005), is common in the central core of Sulawesi and also ranges through the northern peninsula where it can be found in the same habitat and altitude as the closely related Rattus xanthurus in the northeast. At least three species of shrews (Crocidura nigripes, C. rhoditis, and C. elongate), two tree squirrels (Rubrisciurus rubriventer and Prosciurillus murinus), and seven other species of murids (Maxomys musschenbroekii, Maxomys hellwaldii, Lenomys meyeri, Margaretamys beccarii, Haeromys minahasae, Paruromys dominator, and Rattus hoffmanni) occur in the central core of Sulawesi and on the northern peninsula east of Gorontalo. There is nothing in the morphology of specimens in samples of these species to suggest genetic isolation between populations in the central core and those on the eastern portion of the northern peninsula (this report; Musser, ms) and they may represent expansion from central Sulawesi into the northeastern peninsula after drops in sea level that exposed a connecting land mass covered in suitable forest habitats extending from the central core to the northeastern tip of intact Sulawesi. In contrast with these species, Hyosciurus ileile may have never dispersed east of the Gorontalo area. From the early days of Dutch occupation until the present, the northeastern Minahasa district has probably been the focus of more mammal collecting than any other region of Sulawesi, yet no samples of the ground squirrel have ever been obtained.

Gunung Ile-Ile at 1700 m is the highest site from which H. ileile has been collected and is in montane forest. In the central core of the island, 168 m to 1512 m are the elevational extremes documented by voucher material, and those samples came from a region of continuous forest cover extending from tropical lowland evergreen rain forest to lower montane rain forest.

The presence of H. ileile on the northern peninsula in montane forest at 1700 m, nearly 200 m higher than recorded in Sulawesi's central core, may reflect the absence of H. heinrichi from the peninsula. Present samples of H. heinrichi document its distribution in montane forest habitats, not in tropical lowland rain-forest habitats, and its parapatry with H. ileile at the lower boundary of its elevational range and the upper boundary limit of H. ileile. Both are ground squirrels, both are similar in body size and proportions, both exhibit similar pelage coloration, and both feed on Lithocarpus fruit and arthropods. This possible competitive altitudinal pattern should be the subject of careful ecological inquiries both on the northern peninsula and in the central core of the island.

Description

Hyosciurus ileile is of moderate size with a short tail (length of head and body, 215–250 mm; length of tail, 70–125 mm; length of hind foot, 57–60 mm; weight, 293–520 g; LT/LHB  =  49%; extremes for sample from central Sulawesi extracted from table 43). It resembles H. heinrichi in physical build, but is larger and chunky in appearance with a shorter muzzle that appears blunt compared to the long face of H. heinrichi (photographs of a live H. ileile reproduced in figs. 43, 44). Upperparts show more brown tints, underparts are cream.

Fig. 48

Hoplopleura leucomus, female. A, dorsoventral view; B, thoracic sternal plate; C, D, paratergal plates showing slight variation between specimens from two geographic regions (C is from the holotype louse from Labuan Sore in Central Sulawesi, D is from a louse specimen from Rurukan in north Sulawesi); E, genitalia.

Fig. 49

Hoplopleura alstoni, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

As in H. heinrichi, three pairs of teats are typical of H. ileile, one abdominal pair and two inguinal pairs. One female contained two embryos in a left uterine horn.

Views of the skull are provided in figure 37; compare these with those of H. heinrichi on the opposite page in figure 36. Cranial and dental measurements are summarized in table 45.

Comparisons

Hyosciurus ileile has been compared with H. heinrichi in the account of the latter.

Geographic Variation

We have two sets of samples for H. ileile. One consists of two very young adults (the type series) from Gunung Ile-Ile on the northern peninsula. The cheek teeth of both are slightly worn, and the presphenoid-basisphenoid and basisphenoid-basioccipital sutures are open. The other is composed of three samples from the northern part of Sulawesi's central core: three from lowlands in the Sungai Tolewonu region, three from Sungai Sadaunta, and six from Gunung Kanino (five were measured); very young adults, young adults, and adults are contained in these series. Specimens in both sets of samples resemble one another in body size and pelage coloration, except that the tails and hind feet of the two specimens from Gunung Ile-Ile average slightly shorter than those variables in the three samples from the central core of the island (table 43).

Some cranial dimensions are of comparable size in the two sets of samples (length of maxillary molar row, for example; table 45), but others are not. The two squirrels from Gunung Ile-Ile have a slightly shorter facial skeleton and basicranial region than do most of the specimens from Musser's transect. This contrast is reflected in mean values for dimensions related to the muzzle (length of nasals, LN; length of rostrum, LR; projection of nasals and premaxillary beyond the incisors, LPT; and height of rostrum, HR) and back of the skull (postpalatal length, PPL) that are listed in table 45, and the scatter of specimen scores projected onto the first and second principal components extracted from principal-components analysis displayed in figure 45. Covariation in nearly all cranial variables contributes at some intensity to the spread of scores along the first axis, an estimate of increasing size from left to right; especially forceful are the variables associated with length of the muzzle and back of the skull (table 50). Scores for the two squirrels from Gunung Ile-Ile lie on the left, and all but one of the scores representing specimens from the central core are scattered to the right. Of the five scores representing specimens from Gunung Kanino, a single very young adult (AMNH 225549: showing slight wear on the premolars and molars, and open presphenoid-basisphenoid and basisphenoid-basioccipital sutures) clusters with the two points for the squirrels from Gunung Ile-Ile.

Fig. 50

Hoplopleura topapuensis, male. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

TABLE 50

Results of Principal-Components Analysis Contrasting Population Samples of Hyosciurus ileile Principal components are extracted from a covariance matrix of log-transformed values for 18 cranial and 1 dental variable; see figure 45.

Impressive variation in skull size exists within a particular age group, at least in those samples collected along Musser's transect (Sungai Tolewonu, Sungai Sadaunta, and Gunung Kanino). For example, of the 10 skulls measured for the principal-components analysis, five are adults and five are young adults (all have slight wear on the occlusal surfaces of the cheek teeth and the basioccipital-basisphenoid suture and basisphenoid-presphenoid suture are completely open). The largest of the young adults has a skull length of 62.4 mm (AMNH 226497), the smallest is 57.0 mm (AMNH 225459). Skulls from the two squirrels collected on the northern peninsula on Gunung Ile-Ile are closely similar to AMNH 225459 in overall size and general conformation.

To reduce the effect of the adult specimens in the principal-components analysis, we eliminated them and employed only the two young adults from Gunung Ile-Ile and the five young adults from Musser's transect. The pattern of scores within the ordination defined by first and second principal components (not illustrated) is similar to the spread shown in figure 45 that was derived from young adults, adults, and old adults.

Whether the distribution of specimen scores derived from the available material reflects regional variation in cranial dimensions between samples from the northern peninsula and those from Sulawesi's central core, variation concomitant with age, or different gene pools is unclear. We have only two young squirrels from one montane locality at 1700 m on the northern peninsula, and 12 specimens from the central core collected through a range from 168 m to 1512 m. We know nothing about the characteristics of Hyosciurus that may inhabit forests between these sampled regions. Is the montane population of H. ileile on Gunung Ile-Ile characterized by small physical build or are we just seeing the very young adult end of the age spectrum? Is H. ileile restricted to montane habitats on the northern peninsula or does it range into tropical lowland evergreen forests on that peninsula? If H. ileile does inhabit lowland forests on the peninsula, are the phenetic and genetic attributes of these lowland squirrels the same as those in Sulawesi's central core? Or would genetic discontinuity exist between the lowland populations somewhere near the base of the northeastern part of the peninsula and the central core, a break coinciding with that between the tree squirrels Prosciurillus leucomus (peninsular distribution) and P. topapuensis (central core) and macaques M. hecki (peninsular) and M. tonkeana (central core)? Additional and larger samples from both the northern peninsula and the central core are required to answer these questions that bear on unraveling the possible significance of the morphometric variation we document among the present geographic samples.

Ecology

Hyosciurus ileile is diurnal and terrestrial. In the northern part of central Sulawesi, the ground squirrel occurs throughout a range of forest habitats, from the warm and humid lowland tropical evergreen rain forests (environments similar to those shown in figs. 8, 22, and 23) to the cooler lower montane forests (fig. 27; see table 2 for ambient temperatures recorded at various camps through this range of habitats). The squirrels were trapped in streamside habitats and in forests on hills and ridgetops (see table 51 for a summary of habitats at trapping sites). Musser worked in the forest nearly every day at camps scattered from the lowlands to higher altitudes, but outside of those in traps saw the ground squirrel only once, near Tomado. He trapped 12 H. ileile at localities far apart along his transect; by contrast, twice as many H. heinrichi were encountered and within a relatively much smaller area on the transect line. Similar trapping regimes were employed everywhere along the transect.

TABLE 51

Summary of Habitat, at Trapping Sites, Stomach Contents, and Other Relevant Information for Specimens of Hyosciurus ileile Collected by Musser in Central Sulawesi, 1974–1976 Collection locality, specimen numbers, elevation, and month and year of collection are included. Descriptions of the trapping sites and contents of stomachs, slightly edited, are from Musser's field journals (in mammalogy archives at AMNH). Two collection localities (Sungai Sadaunta and Sungai Tolewonu) are in tropical lowland evergreen rain forest. Sites on Gunung Kanino are in lower montane rain forest. All squirrels were caught during the day in Conibear traps (rats taken in the same traps were caught during the night). Unless noted differently, trapping sites were in primary forest formations.

That is why the following particular capture was a pleasant surprise. Musser recorded observations of an adult male H. ileile livetrapped on February 14, 1976, along the Sungai Tolewonu at 152 m. This handsome, beautiful squirrel was at first very nervous when caged, but soon grew accustomed to the enclosure, bumping and biting the sides only if unduly disturbed. He was active during the day, vocalizing in the morning and late afternoon; at night he slept curled on his side on a platform.

This individual's vocalization was unlike that of H. heinrichi and consisted of two different calls. When disturbed, or when he grabbed a beetle larva from Musser's fingers, he would growl “Errr, errr, grrr” in short bursts from deep within his throat; the tree squirrel Rubrisciurus rubriventer growls in a similar way. The only other type of call Musser heard was usually made in mornings and afternoons: a high-pitched squeal, “eeee, eeee,” each squeal lasting 3–5 seconds. A variant was a drawn out single “eeee----e” that started high and dropped to silence, and a double “ee, ee” uttered quickly. All these kinds of squeals resembled the whine of an unoiled machine.

The squirrel quickly learned to drink water through a spout from a bottle, which he used throughout the day. Musser provided him with bait (a ground mixture of rolled oats, raisins, peanut butter, and bacon), nutmeg and ginger fruit, other kinds of fruit that are regularly eaten by Rubrisciurus rubriventer, small adult carabid beetles, small lizards, and earthworms. All were ignored. The only items accepted were large beetle larvae that Musser excavated from rotting trunks and limbs lying on the forest floor, and acorns (fruit from Lithocarpus). The squirrel would grab the larva from Musser's hand, grasp it between his front feet, and proceed to eat the head, then open the thorax and consume the internal organs, but discard the soft abdomen. Adult beetles found in the same rotting wood as the larvae were offered to the squirrel but were ignored.

Musser cut open acorns from the two species of oak growing in the Tolewonu area to determine which species the squirrel preferred. Lithocarpus celebicus, the more common of the two, is a tall canopy tree, or sometimes an emergent, occurring on flat, damp river terraces and hillsides above the river, and here and there on higher slopes below ridgetops. This species was seen only in tropical lowland evergreen rain forest between 30 and 1000 m along Musser's transect. The other oak, Lithocarpus glutinosus, was less frequently encountered, growing on hillsides but apparently absent from wetter areas along stream terraces. Musser identified this species along his transect all the way up to Gunung Kanino. Most of the opened acorns from L. celebicus contained pulp and a small seed. The squirrel grabbed each opened section and quickly ate the seed, then gouged out and ate some of the pulp, but left most of it. Then he was given acorns from L. glutinosus, each of which was packed with a solid nutty seed covered with a very thin pale brown skin, with no pulp at all. The squirrel quickly took them and ate all the contents leaving only the hard husks. He clearly recognized the fruit and ate it voraciously, holding the acorn with his front feet and using the lower incisors to scoop out the contents. The squirrel sat on his haunches as he ate the seed, with his tail curled against his back.

The squirrel was released a few days after capture; he jumped from cage to ground, poked about the camp for a few minutes, and finally fled into the forest uttering a low and guttural series of chucks as he disappeared from sight into the undergrowth.

Hyosciurus ileile, like its montane relative H. heinrichi, is a consumer of fruits and arthropods (tables 51, 57). Acorns (Lithocarpus fruits) and figs seem to be preferred, but other kinds of fruits with large seeds are also taken—the variety of fruits consumed is greater than that of H. heinrichi, at least judged by our samples. Remains of pill bugs (Crustacea, Isopoda), Geophilomorph and Scolopendromorph centipedes, scorpions, orthopterans, occasional ants, ant pupae, adult beetles, and large, long-legged cursorial beetle larvae were found in stomachs, pointing to leaf litter habitats on the ground surface as the source of prey.

The question of why H. ileile seems to be uncommon within its range compared to H. heinrichi needs to be addressed in future ecological studies. Relative abundance of oaks in tropical lowland evergreen rain forest as opposed to montane forests may be one of several factors responsible. Musser, in the process of collecting botanical samples, observed that oaks in the lowlands were widely scattered throughout the forest, usually single trees here and there, occasionally in small groves of three to four trees. Although L. celebicus was seen more frequently than L. glutinosus, neither of the two was common.

Oaks are more abundant in lower and upper montane forests and at least three species are present. Between 1400 and 1700 m on ridgetops and hillsides of Gunung Kanino and the lower slopes of Gunung Nokilalaki, L. glutinosus and L. elegans occur with chestnuts (Castanopsis acuminatissima) to form extensive groves in which some other trees are intermingled (Calophylum, for example). Those two oaks are replaced by Lithocarpus havilandii on higher slopes and the summit of Gunung Nokilalaki where it comprises one of the most common components of the forest, even forming extensive groves in places.

Both species of ground squirrels consume oak fruit and arthropods found in leaf litter (see table 57). Within the context of the distribution of oaks described above, population size of H. ileile in lowland forests may be constrained by the lower abundance of oaks compared to their higher abundance in montane forest habitats. These observations represent unquantified anecdotal information, but provide a hypothesis that could be tested by results from careful ecological inquiries.

Gunung Ile-Ile or elsewhere in Pegunungan Peleleh, which forms the mountainous backbone of the northwestern portion of the northern peninsula, would be an ideal place for a transect study extending from the lowlands into the mountain forests. Hyosciurus ileile has been taken in a high montane habitat; presumably it also occurs at lower altitudes down through tropical lowland evergreen rain forest, and present data indicate H. heinrichi is absent from the northern peninsula. In the absence of H. heinrichi, is the population size of H. ileile greater in the montane habitats and reduced in lowland forests? And along such a transect line, does the relative abundance of oak species resemble that observed by Musser in the central core of the island?

Ectoparasites

In addition to a host-specific sucking louse, Hoplopleura ileile, n. sp., this ground squirrel is parasitized by immature stages (larvae and/or nymphs) of ticks (Acari, Ixodidae) belonging to the genera Dermacentor and Haemaphysalis (Durden et al., 2008; also see table 56 and the ectoparasites account for Rubrisciurus rubriventer). Further, ectoparasitic laelapid mites were recovered from pelts AMNH 223540 and 225460, both from Gunung Kanino in central Sulawesi at elevations of 1402 and 1463 m in the 1970s.

Sympatry

The range of H. ileile on the northern peninsula of Sulawesi overlaps the ranges of Prosciurillus leucomus, P. murinus, and Rubrisciurus rubriventer (table 6). On Sulawesi's central core, the range overlaps those of P. topapuensis, P. murinus, and R. rubrisciurus (table 6). Along his transect in the northern portion of central Sulawesi, Musser trapped H. ileile in the same traplines, and sometimes in the same traps, as P. topapuensis, P. murinus, and R. rubrisciurus (table 51). See the account of H. heinrichi for the topographic relationships between the geographic and altitudinal distributions of H. ileile and H. heinrichi.

Synonyms

None.

We leave our accounting of Sulawesi's endemic species of squirrels and turn to describing samples that represent two species indigenous not to Sulawesi but to forested islands, peninsulae, and mainland in the Indomalayan region west of Sulawesi. Their occurrence on the island represents anthropogenic introductions, likely as pets. We did not survey the skins of these specimens for sucking lice.

Lectotype and Type Locality

The lectotype of Sciurus microtis is an adult female (RMNH 13349, specimen “e” in Jentink's, [1888: 29] catalog) obtained by J.E. Teysmann in 1877. Jentink (1888: 29) incorrectly indicated 1887 to be the year the specimens were collected. Chris Smeenk writes in his unpublished catalog of Leiden mammalian types: “Teysmann worked on Salayar from 16 November to 11 December 1877 (Van Steenis-Kruseman, 1950: 524). The year 1878 given by Jentink (1887, 1888) thus refers to the year when the material was received in Leiden.” He explained (in litt., 2008) that “ Jentink (or his predecessors, in this case Schlegel) very often confused the years of collection and reception.” The lectotype consists of a skin mounted in a live pose and a skull (extracted from the mount after Jentink's tenure at Leiden). The skin is overstuffed, leaving an open seam on the head, and the tail is missing. The skull lacks part of the braincase but is in the best condition and the most complete of all the six syntypes.

Specimen “e” was one of six specimens cataloged as types ( =  syntypes) by Jentink (1888: 29). Following Chris Smeenk's suggestion (in litt., 2008), we select specimen “e” as the lectotype, following the rules promulgated in Article 74.1 of the Code (ICZN, 1999: 82). The other five, all collected by J.E. Teysmann in November–December, 1877, become paralectotypes: (1) specimen “a” (Jentink, 1887: 193, 1888: 29), RMNH 13345, an adult male, skin mounted in live pose and extracted incomplete skull; (2) specimen “b” (Jentink, 1887: 193, 1888: 29), RMNH 13346, an adult male, skin mounted in live pose and extracted partial skull; (3) specimen “c” (Jentink, 1887: 193, 1888: 29), RMNH 13347, an adult male, skin mounted in live pose and extracted incomplete skull; (4) specimen “d” (Jentink, 1888: 29), RMNH 13348, an adult female, skin mounted in live pose and extracted incomplete skull; (5) specimen “f” (Jentink, 1888: 29), RMNH 13350, an adult female, skin mounted in live pose and extracted incomplete skull.

The type locality is Pulau Salayar (06°05′S, 120°30′E) off the southern coast of the southwestern peninsula (see one of the distribution maps for any species of the endemic squirrels), Propinsi Sulawesi Selatan, Indonesia.

Remarks

In addition to the lectotype and five paralectotypes, we have also examined the six specimens discussed by Sody (1949: 92): MZB 6105–6110.

In his description, Jentink (1879: 41) noted that microtis was similar to “Sciurus nigrovittatus” ( =  Callosciurus nigrovittatus) in its fur markings, and described the species as follows:

Major checklists of mammals have identified Jentink's microtis as a population of Callosciurus notatus occurring on Pulau Salayar (Ellerman, 1940; Laurie and Hill, 1954; Corbet and Hill, 1992; Hoffmann et al., 1993; Thorington and Hoffmann, 2005). The species is of medium body size with dark brown upperparts, buff and black stripes on sides of the body and underparts ranging from gray to chestnut (see measurements and the illustrations in Medway, 1969, and Payne et al., 1985). Callosciurus notatus has been documented from peninsular Thailand, the Malay Peninsula; the larger islands of Sumatra, Java, Bali, and Borneo, and some smaller islands on the Sunda Shelf; and Lombok and Salayar to the east of the Shelf (Kitchener et al., 1980; Corbet and Hill, 1992: 291). At least 77 scientific names, originally identifying separate species, or subspecies of notatus, have been attached to C. notatus, but as Corbet and Hill (1992: 291) noted,

Corbet and Hill wrote of the dull lateral stripes of squirrels in the Salayar sample, and their dull buff venters, which closely resemble some squirrels in samples from Java. The variation in color of underparts of the specimens we examined range from grayish buff to pale orange, and do match samples from Java we studied, as does the intensity of the lateral stripes.

A careful and comprehensive analysis of geographic variation in pelage coloration, morphometric traits, and molecular characteristics for C. notatus has yet to be realized. Results of such a study may identifiy discrete populations that represent different species, possibly assemble related geographic populations, and hopefully point to the geographic origin of the populations on Lombok and Salayar. The occurrence of C. notatus on those two islands east of the Sunda Shelf may represent natural dispersal, but introduction by humans seems more likely. Chris Smeenk (in litt., 2009) writes us that,

That the species could be an anthropogenic introduction to Salayar is suggested by its habitat and the apparent absence of nearly all endemic Sulawesi mammal species from the island. Today little of the original semi-evergreen rain forest remains on Salayar, and most of the island consists of cleared or cultivated land (see map 8d in MacKinnon, 1997). We have no information about the environment on Salayar where the specimens were collected, but elsewhere within its range C. notatus is abundant in gardens, plantations, and secondary forests. On Borneo the squirrel “…can live and breed entirely in monoculture plantations” (Payne et al., 1985: 236). Davis (1962: 78) wrote of Bornean populations: “This species does not appear to be common in the interior of the primary forest, but is abundant around the edges, in clearings, and in secondary growth. It is often seen in towns and cities, and does considerable damage to coconut and rubber plantations.” In our experience, the endemic species of Rubrisciurus, Prosciurillus, and Hyosciurus have been encountered only in primary forest habitats. No sample of any species in those three genera has ever been collected on Pulau Salayar, and of all the species of mammals endemic to Sulawesi, only a tarsier has been recorded from the island (Groves, 2005: 128).

Although the origin of the Salayar population is unresolved, we do know that C. notatus is a member of the Sundaic mammalian fauna, that it has never been recorded from the mainland of Sulawesi or any other offshore island than Pulau Salayar, and that it is phylogenetically not closely related to the endemic Sulawesian species of Rubrisciurus, Prosciurillus, and Hyosciurus.

Callosciurus prevostii (Desmarest, 1822)

Sciurus erythromelas Temminck, 1853: 248.

Sciurus erythrogenys Schlegel, 1863: 29, pl. 2, fig. 3; not Waterhouse (1942 [1943]).

Sciurus Schlegelii Gray, 1867: 278 ( =  Macroxus Schlegelii Gray, 1867: 278).

The three scientific names are attached to two specimens that differ conspicuously in coloration of fur, but likely represent the same species: Callosciurus prevostii. We explain our reasons for this allocation in the following paragraphs.

The lectotype of Sciurus erythromelas is an adult male (RMNH 13378, specimen “bb” in Jentink's [1888: 27] catalog) obtained by E.A. Forsten sometime betwen 1840 and 1842. The lectotype consists of a skin mounted in a live pose and a skull (extracted from the mount after Jentink's tenure at Leiden). The skin is in very good condition except for slight damage to the mouth caused when the skull was extracted. The occiput, one ectotympanic bulla, and one zygomatic arch are missing from an otherwise complete skull. Specimen “bb” was one of two specimens cataloged as types ( =  syntypes) by Jentink (1888: 27). Following Chris Smeenk's suggestion (“It is perfect for a lectotype,” in litt., 2009), we select specimen “bb” as the lectotype, following the rules promulgated in Article 74.1 of the Code (ICZN, 1999: 82). The type locality is Kema (01°22′N, 125°03′E; locality 8 in gazetteer for Prosciurillus leucomus and map in fig. 11), near sea level on the coastal plain of the northeastern end of the northern peninsula, Propinsi Sulawesi Utara, Indonesia. RMNH 13378 is also the holotype of Sciurus erythrogenys Schlegel, 1863 and Macroxus schlegelii Gray, 1867 (see the discussion to follow).

The other specimen, also collected by E.A. Forsten between 1840 and 1842, but from Manado (01°30′N, 124°50′E; locality 4 in gazetteer for Prosciurillus leucomus and map in fig. 11) on the coastal plain near sea level, is the paralectotype of Sciurus erythromelas: specimen“cc” (Jentink, 1888: 27), RMNH 13379, an adult male. The skin, mounted in a live pose with the skull still in the skin, is in good condition, and retains its bright color pattern.

Chris Smeenk is preparing a catalog of the “Type-specimens of recent mammals in the National Museum of Natural History, Leiden” and gave us permission to quote his account for Sciurus erythromelas, which is the best place to begin our discussion of the type specimens. Chris writes that:

Ten years after Temminck's account was published (see appendix 6 for Temminck's description in the original French), Schlegel's [1863: 29] description of Sciurus erythrogenys appeared. Schlegel regarded the squirrels from NE Celebes described by Temminck (1853: 248) as Sciurus erythromelas to represent two distinct species. He restricted the name S. erythromelas to the specimen from Manado (RMNH 13379) and described the squirrel collected at Kema (RMNH 13378) as S. erythrogenys, named for its reddish cheeks (the description in the original French is provided in appendix 7).

Gray (1867: 278) later renamed the same specimen: “Sc. schlegelii (with cheeks red), Sc. erythrogenys, Schlegel, l. c. t. 2. f. 3 (1863), not Waterhouse” because erythrogenys was proposed earlier by Waterhouse (1842 [1843]) for the African red-cheeked rope squirrel Funisciurus leucogenys (Waterhouse, 1842). As Thorington and Hoffmann (2005: 792) explained, “Waterhouse (1842 [1843]) renamed this species [F. leucogenys] erythrogenys, ‘red-cheeked’ in an attempt to replace the inappropriate name leucogenys, ‘white-cheeked.’ This is an unjustified emendation.”

Gray proposed schlegelii within his account of Macroxus atrocapillus ( =  Sciurus atricapillus Schlegel, 1863; incorrectly quoted by Gray as “atrocapilla”; atrocapillus is currently treated as either a synonym of Callosciurus prevostii or a valid subspecies, C. p. atrocapillus; Payne et al., 1985; Corbet and Hill, 1992; Thorington and Hoffmann, 2005). Gray's wording, “Sc. Schlegelii (with cheeks red), Sc. erythrogenys, Schlegel, l. c. t. 2. f. 3 (1863), not Waterhouse,” was meant to explicitly identify schlegelii as a replacement name for Schlegel's erythrogenys within Sciurus, the genus in which Schlegel described erythrogenys. Gray used Macroxus for species of Oriental squirrels, not Sciurus, so the correct combination for his replacement name is Macroxus schlegelii (we are grateful to Chris Smeenk and Al Gardner for their insight into this nomenclatural issue).

RMNH 13378 is the holotype of both Sciurus erythrogenys Schlegel, 1863, and Macroxus schlegelii Gray, 1867, as well as the lectotype of Sciurus erythromelas Temminck, 1853 (see above).

The two specimens are differently colored. The upperparts of the head and body as well as the tail of the lectotype of Sciurus erythromelas (RMNH 13378 from Kema) is dark brown speckled with buff and black, including the outside of the limbs. Sides of the body are marked by a whitish gray stripe above a black stripe. The underparts are reddish orange, which extends to the inside of the front and hind limb but not to the feet, which are black, and the cheeks and throat are orange-red.

The paralectotype of Sciurus erythromelas (RMNH 13379 from Manado) is appreciably darker. The head and back, back of the thighs, and tail are blackish. A single pale stripe (brownish black speckled with gray) marks each side of the body (no black stripe). The area around the mouth, cheeks, shoulder, upper arms, and front of the thighs are brownish black speckled with buff (appears grizzled). The underparts from chin to base of the tail, including most of the forearms (the blackish upperparts extend along the outside of the forearms as a narrow blackish stripe towards the front feet) are dark reddish orange; sides of the feet and parts of the dorsal surfaces are the same color (although tops of the hind feet are washed with brownish black).

To us, the color patterns of the two types are reminiscent of Callosciurus prevostii, a Sundaic endemic occurring on peninsular Thailand and Malaya, the larger Sundaic islands of Sumatra and Borneo, and smaller islands on the Sunda Shelf, but not Java (Corbet and Hill, 1992; Thorington and Hoffmann, 2005). The species is medium in body size (length of head and body, 200–267 mm; length of tail, 202–273 mm; length of hind foot, 45–61 mm; weight, 250–500 g; see Medway, 1969; Payne et al., 1985), physically smaller than the Sulawesian Rubrisciurus rubriventer, but larger than species in the Prosciurillus leucomus group (see table 3). On Borneo, tall and secondary forests are the habitat of C. prevostii, where it stays mostly in the upper canopy, descending to the ground when necessary to cross gaps in the canopy; it will also enter gardens and plantations next to tall forest (Davis, 1962; Payne et al., 1985: 234). In parts of the Malay Peninsula, the squirrel is locally common in oil plantations and adjacent forest, and is “popular as a pet because of its bright coloration” (Medway, 1969: 59).

Probably no other species of Callosciurus is as geographically variable in color patterns of the fur, not only among peninsular and insular landmasses but also within large islands, especially so among populations on Borneo (Corbet and Hill, 1992; Musser's study of specimens representing Indomalayan species). Payne et al. (1985; pl. 24) provide color renditions of the primary chromatic patterns found among Bornean populations and their general distribution on the island. Some populations exhibit intergradation in these patterns, other populations isolated by rivers apparently do not.

In his list of squirrel specimens in Leiden, and his catalog of mammals in that institution, Jentink (1883: 132, 1888: 27, respectively) listed the types of erythromelas and erythrogenys (including schlegelii) under “Sciurus prevostii.” Later checklists arranged erythromelas and schlegelii each as a subspecies of Callosciurus prevostii with both occurring on Sulawesi (Ellerman, 1940: 367; Laurie and Hill, 1954: 92) or associated with Bornean C. prevostii but unassigned as to subspecies status (Hoffmann et al., 1993: 423; Thorington and Hoffmann, 2005: 279); none of these checklists published after Jentink's catalog listed Schlegel's erythrogenys.

We agree with Jentink's (1888: 27) identification of the lectotype and paralectotype of erythromelas as examples of Callosciurus prevostii. The population of C. prevostii living in northern Borneo in Sabah and northeastern Sarawak, C. p. pluto, is black with bright reddish orange underparts, and some specimens show a weak whitish body stripe (see Payne et al., 1985, pl. 24); the coloration closely resembles the paralectotype of Sciurus erythromelas (RMNH 13379) from Manado; the minor differences could easily be ascribed to individual variation.

The brighter lectotype of Sciurus erythromelas could be a color variant of Bornean C. prevostii. It does not exactly match any of the color examples illustrated by Payne et al. (1985, pl. 24), but its color pattern does fall somewhere between that illustrated for C. p. atricapillus from eastern Sarawak (possessing dark hind feet and limbs) and that for C. p. caroli from farther to the northeast in Sarawak (with orange-red throat and cheeks). Corbet and Hill (1992: 290–291) listed S. erythromelas (along with S. schlegelii) as a synonym, with question, of Callosciurus baluensis, an endemic of the north Bornean mountains in Sabah and Sarawak, with an altitudinal range of 300 to 2000 m: “The type of erythromelas (Leiden Museum) matches Bornean C. baluensis rather closely in pelage but has more orange-brown on the cheeks.” Musser examined the holotype of baluensis, and other specimens, including the holotype of baramensis, the other name associated with C. baluensis. None of the examples of C. baluensis has the orange-red cheeks and black feet seen in the lectotype of Sciurus erythromelas.

For now we prefer to associate erythromelas (along with erythrogenys and schlegelii) with Bornean C. prevostii rather than C. baluensis. This identity can be tested in two ways. Although the skull of the lectotype of erythromelas is damaged, enough of its dimensions could be measured and the values compared with those obtained from samples of C. baluensis and geographic samples of C. prevostii from Borneo in a multivariate analysis (principal-components analysis, for example). Results from analyses of DNA sequences extracted from hairs or bits of dry skin from the lectotype of erythromelas and samples of C. baluensis and C. prevostii would also be revealing. If in the future, the lectotype of Sciurus erythromelas can be unambiguously identified as an example of C. baluensis, that latter name will have to be changed to Callosciurus erythromelas, which would then be a species with its indigenous range in northern Borneo, but its type locality outside of that range in northeastern Sulawesi.

We do not know how many specimens (and their collection localities) Temminck (1853) originally used for his description of Sciurus erythromelas. We do know that two remain in the collection at Leiden, that each is different in color pattern, that no other specimen resembling either one has ever been collected on Sulawesi since Forsten's activities between 1840 and 1842, and that the two types do not represent any species of squirrel truly endemic to Sulawesi. Both specimens are likely examples of geographic variation described for the populations of Callosciurus prevostii on Borneo. We suspect the material obtained by Forsten to have originally been transported as pets from Borneo to the Minahasa region (in which the coastal towns of Kema and Manado are located).

With this last account, we leave the squirrels and turn to the eight species of sucking lice parasitizing eight of the 10 species of Sulawesi's endemic squirrels. All samples of lice represent new species, and their descriptions are contained in the following segment of our report.

Holotype and Type Locality

Male and allotype female ex male Rubrisciurus rubriventer (AMNH 225491; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by G.G. Musser at 4960 ft (1512 m) on Gunung Kanino (1°17′S, 120°08′E; see gazetteer and fig. 5), Propinsi Sulawesi Tengah, Indonesia, on 31 January 1975. The holotype is deposited in USNM.

Referred Specimens

An additional 5 males, 11 females, and 4 nymphs from the same pelt as the holotype and allotype; two nymphs ex male R. rubriventer (AMNH 224052) collected by G.G. Musser at 675 m at Sungai Sadaunta (1°23′S, 119°58′E), central Sulawesi on 9 February, 1974; one female ex female R. rubriventer (identified in the field by L.A. Durden and I.A. Hanski) collected by I.A. Hanski at ca. 1100 m on Gunung Maujat (0°45′N, 124°25′E), on the northern peninsula of Sulawesi (Sulawesi Utara), on 5 February, 1985; one male ex female R. rubriventer (BM 40.674) collected by W.J.C. Frost at 4000 ft (1220 m) in the Luartes Range, Pegunungan Quarles, Bulu [ =  Gunung] Karua (referred to as “Rantekaroa, Quarles Mt.” on specimen tags), 02°56′S, 119°39′E), central Sulawesi, on 13 December, 1939; one male ex female R. rubriventer (AMNH 101316) collected by G. Heinrich at 50 m at Wawo (3°41′S, 121°02′E), on the southeastern peninsula of Sulawesi, on 23 January, 1932. Paratypes are deposited in AMNH, BMNH, LAD, and USNM.

Distribution

Known only from the five collections listed above, all from Rubrisciurus rubriventer. Hoplopleura rubrisciuri probably parasitizes R. rubriventer throughout its geographic and altitudinal ranges (see fig. 11 and table 4).

Etymology

This louse is named for the monotypic host genus.

Diagnosis

Hoplopleura rubrisciuri is a distinctive louse. It can be distinguished from all other species of Hoplopleura using a combination of the following characters: (1) the absence of dorsal abdominal plates in both sexes and the absence of sternal abdominal plates (between the 3rd sternal plate and the subgenital plate), in the female, N.B., a wrinkled texture is characteristic of the abdomen in some specimens that superficially gives the impression of numerous narrow plates; (2) the presence of one short and one long apical seta on paratergal plate II and of two long apical setae on each of paratergal plates III–VIII in both sexes; (3) the shape and proportions of the thoracic sternal plate and of the genitalic structures in both sexes.

Description

Abbreviations used here and in descriptions of the other species of lice to follow are explained in Specimens and Methods.

Male (fig. 46A–D). Length of holotype 1.02 mm (mean for series 1.01, range 0.92–1.08, N  =  8). Head and thorax well sclerotized.

Fig. 51

Hoplopleura topapuensis, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head. Slightly longer than wide with broadly rounded anterior apex; 3 SuHS, 4 DMHS, 1 DPoCHS, 1 SpAtHS, 2 ApHS (1 dorsal, 1 ventral), 4 AnMHS (2 dorsal, 2 ventral), 2–3 VPaHS, and 1 VPHS on each side; DPHS fairly long, extending to thoracic spiracle, with 1 DAcHS medial to DPHS. Antenna. 5-segmented with basal segment much larger than second segment, slightly wider than long.

Thorax. About as broad as long; thoracic sternal plate (fig. 46B) blunt anteriorly and tapering to broad apex posteriorly; mesothoracic spiracle moderate in size (0.020 mm in diameter) with one small DMsS and one fairly long DPTS (0.14 mm in length) medial to spiracle. Legs. Forelegs small, each with narrow acuminate claw; hind coxa and claw robust; midlegs intermediate in size between fore and hindlegs.

Abdomen. Wider than thorax; no dorsal plates; two plates per segment ventrally on segments 2–6; first ventral plate small, plates 2 and 3 broad, well sclerotized, and extending laterally to articulate with corresponding paratergal plates; ventral plate 3 with two robust lateral setae on each side (three on one side in one specimen); ventral plates 4–12 narrow and poorly sclerotized; one row of DCAS per segment dorsally, first row with 2 DCAS, 2nd row with 4 DCAS, rows 3 and 8 each with 6 DCAS, rows 4–7 each with 10–17 DCAS; most DCAS long and thin except for a few dagger-shaped lateral setae; 11 rows of 7–10 StAS ventrally; 1 VLAS lateral to each of ventral plates 8–11 on each side. Paratergal plates (fig. 46C) present on segments 1–8: plate I lacking setae; plate II with one long and one short apical seta; plates III–VIII each with two long apical setae; plates II–V subtriangular and with both apices developed into points; plates III–VII each with moderate-size spiracle.

Genitalia (fig. 46D). Long subgenital plate (extending anteriorly to level of paratergal plate VI in most specimens) with characteristic undulating lateral margins (as shown in fig. 46A); aedeagal basal apodeme slightly longer than parameres; parameres broad, curved, and tapering apically; pseudopenis short, barely extending beyond apices of parameres.

Female (fig. 47A–D). Length of allotype 1.31 mm (mean for series 1.18, range 0.92–1.33, N  =  13).

Fig. 52

Hoplopleura murinus, male. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head, thorax, and legs. As in male unless indicated otherwise. 1 DAnCHS and 2 SpAtHS on each side of head. Thoracic sternal plate (fig. 47B) similar to that of male but slightly broader.

Abdomen. Wider than thorax; lacking dorsal plates; ventrally with only three anterior plates (plate 1 small, plates 2 and 3 both broad and articulating with corresponding paratergal plates) and subgenital plate; 16–17 rows of DCAS, first and last rows each with two setae, row 2 with four setae, rows 3–6 each with 6–8 setae, and rows 9–15/16 each with 8–13 setae; DCAS in rows 1–4 and in posterior three rows long and narrow; most DCAS in rows 5–13/14 dagger-shaped; 7–8 StAS on ventral plates 2–3; two robust lateral setae on each side on plate 3; 13–14 rows of VCAS posterior to plate 3 each with 7–11 setae; most VCAS dagger-shaped. Paratergal plates (fig. 47C) as in male except for minor differences in shapes of plates as illustated.

Genitalia (fig. 47D). Subgenital plate with deep lateral indentation on each side and four long setae (two on each side) on anterior arms of plate; eight small setae on subgenital plate (four central and two situated proximally on each posterior arm); gonopod VIII with three apical setae of moderate length; gonopod IX with one short stout seta; vulvar fimbriae present.

Remarks

Hoplopleura sp. D listed by Durden (1986) is Hoplopleura rubrisciuri.

Hoplopleura leucomus, new species

Holotype and Type Locality

Female ex male Prosciurillus leucomus (USNM 218077; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by H.C. Raven at 200 m at Labuan Sore (00°37′S, 120°03′E; see gazetteer and fig. 11), Propensi Sulawesi Tengah, Indonesia on 1 December, 1916. The holotype is deposited in the USNM.

Referred Specimens

In addition to the holotype female, two more female specimens, one from the same host (USNM 218077) as the holotype, the other ex male Prosciurillus leucomus (AMNH 196566) collected by G. Heinrich at 900 m at Rurukan (01°21′N, 124°52′E; see gazetteer and fig. 11), Propensi Sulawesi Utara, Indonesia on 22 January 1931.

Distribution

Hoplopleura leucomus is known only from Prosciurillus leucomus, which is recorded from voucher hosts collected at 200 and 900 m. This tree squirrel occurs throughout lowland and montane altitudes in the northern peninsula of Sulawesi and on Pulau Lembeh off the northeastern coast (see fig. 11 and table 4).

Etymology

Named for the specific epithet of the host species.

Diagnosis

Females of Hoplopleura leucomus can be distinguished from females of all other species of Hoplopleura using a combination of the following characters of the female genitalia and associated structures, which are all shown in figure 48E: (1) the distinct shape of the subgenital plate which appears as two laterally elongate plates that are connected medially; (2) the presence of two long setae laterally on each side of the upper section of the subgenital plate together with four central setae (two lateral setae of medium size, two small central setae) in the anterior portion of the lower section of the subgenital plate; (3) the elongate shape and setation (especially the more recessed insertion of the middle of the three setae) of the gonopods VIII. Females of Hoplopleura leucomus have morphological similarities to females of the other species of Hoplopleura described from Sulawesi squirrels in this report in that the subgenital plates all show tendencies toward being separated into two major sections, one anterior and one posterior. In some species, the plate sections are joined medially whereas in others the plates are completely separated. This subgenital plate conformation is rare in females of other species of Hoplopleura regardless of their host(s) or geographic distribution. Although females of all eight of the species of Hoplopleura we describe from Sulawesi squirrels in this report show this morphological trend, a glance at the plates of the females for each of the eight species will immediately show that the species are all very easily separated using only the distinctive morphology and setation of this structure.

Fig. 53

Hoplopleura murinus, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Description

Female (fig. 48A–E). Length of holotype 1.22 mm (mean for series 1.30; range 1.21–1.47, N  =  3). Head, thorax, and abdomen well sclerotized.

Head. Longer than wide with broadly rounded anterior apex; 2 SuHS, 4 DMHS, 1 DAnCHS, 1 SpAtHS, 3–4 AnMHS, and 1 VPHS on each side; DPHS fairly long, extending to mesothoracic spiracle, with 1 DAcHS medial to DPHS on each side. Antennae. 5-segmented with basal segment much wider than second segment, wider than long; second segment elongate.

Thorax. Slightly broader than long; thoracic sternal plate (fig. 48B) with broadly rounded anterior apex, tapering, broadly rounded posterior apex, and broadly rounded lateral margins; mesothoracic spiracle moderate in size (0.019 mm in diameter); DPTS moderate in length (0.12 mm) almost extending to mid region of level of paratergal plate I; no DMsS evident. Legs. Fore and mid coxae subtriangular; forelegs small each with narrow acuminate claw; hindlegs robust each with broad acuminate claw; midlegs intermediate in size between fore and hind legs.

Abdomen. Wider than thorax; 15 plates dorsally comprising three narrow plates on each of segments 4–7, two narrow plates on segment 8 and one broad, curved plate posteriorly; no dorsal plates on segments 1–3; one broad plate per segment ventrally on each of segments 2 and 3; three narrow plates per segment ventrally on each of segments 4–7, and one narrow plate on segment 8; first row of DCAS with two long, thin setae, second and third rows each with four long, thin DCAS, followed by three rows of long, slightly stouter TeAS each with 8–10 TeAS and then by 11 rows of 8–10 dagger-shaped TeAS, and one row of six long, thin TeAS; 10 rows of 1–2 DLAS on each side between segments 4–8; first ventral plate without setae; other ventral plates anterior to subgenital plate each with 8–10 StAS; ventral plates 2 and 3 each articulating with corresponding paratergal plates; ventral plate 2 with three stout lateral StAS on one side (as shown in fig. 48A; two on the other side) and three narrow medial StAS; ventral plate 3 with two robust lateral StAS on each side and three narrow medial StAS; ventral plates 4–16 all with dagger-shaped StAS. Paratergal plates (fig. 48C, D, showing variation) present on segments 1–8: plate II with one long apical seta and one of intermediate length; plate III with two apical setae of intermediate length; plates IV–VI each with one apical seta of intermediate length and the other shorter in length (especially in specimens from Labuan Sore in central Sulawesi as shown in fig. 48C); plates VII and VIII each with two long apical setae; plates I–VI subtriangular; plates II–VI each with both apical angles produced into points; plates III–VII each with moderate size spiracle.

Genitalia (fig. 48E). Subgenital plate with deep lateral indentation on each side and appearance of two separate plates joined medially; two long lateral setae on each anterior arm of subgenital plate; one seta of intermediate length on each side on posterior demarcation of area where two plates appear to be joined, and two small medial setae; gonopods VIII with three apical setae with the middle of these three setae being recessed laterally from plate margin and posterior seta slightly larger than other two setae; gonopod IX with one stout seta; vulvar fimbriae distinct.

Remarks

Often, male genitalia have important distinguishing characters that delineate different species of congeneric sucking lice. Unfortunately, no males of H. leucomus were available for study. Nevertheless, we decided to describe this species based only on female specimens for two reasons. First, as discussed above, the subgenital plate and its associated setae are highly distinctive for this new species as is the subgenital plate morphology for each of the squirrel-associated lice we describe in this report. Secondly, Hoplopleura leucomus likely cospeciated with its host, Prosciurillus leucomus; that host along with each of the other seven Sulawesi squirrel species from which we obtained lice has a unique species of louse. The slight differences we note between the lengths of apical setae on some of the paratergal plates (see fig. 48C, D) on lice collected from Prosciurillus leucomus from different geographic regions are minor and reflect variation within the limits of a single species. The distinctive female genitalic structures, especially of the subgenital plate and its associated setae, are taxonomically more important and are the same in all three specimens we examined regardless of geographic origin. Obviously, it will be important to collect and describe the male of this species and to compare the morphology of lice from P. leucomus from different localities if more specimens become available. Molecular analyses using fresh louse samples would also be desirable.

Hoplopleura alstoni, new species

Holotype and Type Locality

Female ex female Prosciurillus alstoni (USNM 219519; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by H.C. Raven at 31 m at Pinedapa (01°25′S, 120°35′E; see gazetteer and fig. 11), Propensi Sulawesi Tengah, Indonesia on 15 February, 1918. The holotype is deposited in the USNM.

Referred Specimens

The holotype is the only example of the species.

Distribution

Hoplopleura alstoni is known only from Prosciurillus alstoni, which is recorded from a voucher host collected at 31 m. The tree squirrel is found at lowland elevations in the northeastern portion of the central core of Sulawesi, its east-central arm, and the southeastern peninsula and offshore islands (see fig. 11 and table 4).

Etymology

Named for the specific epithet of the host species.

Diagnosis

The female of Hoplopleura alstoni can be distinguished from females of all other species of Hoplopleura using a combination of the following characters: (1) the shape and length of the apical paratergal setae; (2) the almost flat anterior apex of the head; (3) the distinctive shape, proportions, and setation of the genitalia (fig. 49D), especially the shape of the subgenital plate and the positions and lengths of its associated setae. Females of all eight of the species of Hoplopleura described from Sulawesi squirrels in this report are easily distinguished from each other (and from all other species of Hoplopleura) by the distinctive shapes of their subgenital plates and the characteristics (positions and lengths) of the setae attached to these plates.

Fig. 54

Hoplopleura abstrusus, male. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Description

Female (fig. 49A–D). Length of holotype 1.43 mm. Head, thorax, and abdomen well sclerotized.

Head. Longer than wide with blunt, almost flat, anterior apex; 2 SuHS, 3 DMHS, 1 DAnCHS, 3 AnMHS, and 1 VPHS on each side; DPHS fairly long, extending to mesothoracic spiracle, with 1 DAcHS medial to DPHS. Antennae. 5-segmented with basal segment much wider than second segment, wider than long; second segment elongate.

Thorax. Slightly broader than long; thoracic sternal plate (fig. 49B) with broadly rounded anterior apex, tapering, fairly broadly rounded posterior apex and broadly rounded lateral margins; mesothoracic spiracle moderate in size (0.021 mm in diameter); DPTS fairly long (0.16 mm), extending to mid-region of paratergal plate II; no DMsS evident. Legs. Fore and mid coxae subtriangular; forelegs small each with narrow acuminate claw; hindlegs robust each with broad acuminate claw; midlegs intermediate in size between fore and hind legs.

Abdomen. Wider than thorax; 15 plates dorsally with three narrow plates on each of segments 4–7, two narrow plates on segment 8, and one broad plate on segment 9; 16 plates ventrally anterior to subgenital plate with one small plate on segment 1, one broad plate on each of segments 2 and 3, three narrow plates on each of segments 4–7, and one narrow plate on segment 8; first and second rows of DCAS each with two long narrow setae, third row with four long narrow DCAS, followed by 14 rows of TeAS each with 6–9 dagger-shaped setae and then by one row of six narrow TeAS; 11 rows of 1–2 DLAS on each on each side extending from segments 4–8; first ventral plate without setae; ventral plates 2–16 each with 6–10 StAS; ventral plate 2 with six long, narrow StAS; ventral plate 3 with two robust StAS on each side and three narrow medial StAS; ventral plates 4–16 each with dagger-shaped StAS; plates 2 and 3 each articulating with corresponding paratergal plates. Paratergal plates (fig. 49C) present on segments 1–8: plate II with one apical seta of intermediate length but with other apical seta broken at base (on both sides); plates III–VI each with two apical setae of intermediate length but with one seta slightly longer than other seta on each plate; plates VII and VIII each with two long apical setae; all plates subtriangular; plates II–VI each with both apical angles produced into points; plates III–VII each with moderate size spiracle.

Genitalia (fig. 49D). Subgenital plate separated into two laterally elongate, broad sections with anterior plate distinctly larger than posterior plate; anterior section of subgenital plate curved with posterior, medial, broadly rounded apex bearing eight setae consisting of two setae of intermediate length on each side and four small medial setae; two long lateral setae also present on each side of anterior section of subgenital plate; posterior section of subgenital plate subeliptical and with two fairly small lateral setae on each side; gonopods VIII each with three apical setae increasing in length from anterior to posterior; gonopods IX each with one stout seta; vulvar fimbriae indistinct.

Remarks

Because only the holotype female was available for this new species, many of the remarks made above for Hoplopleura leucomus, for which only three females were available, could be repeated here. We decided to describe H. alstoni based only on the holotype female because the subgenital plate and its associated setae are highly distinctive and because this louse evidently cospeciated with its host. The result of this apparent cospeciation is that each of the eight Sulawesi squirrel species from which we obtained lice has a unique species of louse. Obviously, the male of Hoplopleura alstoni should be described if additional material becomes available.

Hoplopleura topapuensis, new species

Holotype and Type Locality

Male ex male Prosciurillus topapuensis (USNM 219493; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by H.C. Raven at 1800 m at Rano Rano (1°30′S, 120°28′E; see gazetteer and fig. 11), Propensi Sulawesi Tengah, Indonesia on 21 December, 1917. The holotype is deposited in USNM.

Referred Specimens

One additional male, 12 females (including allotype), 1 nymph ex male P. topapuensis (AMNH 225505) collected by G.G. Musser at 4900 ft (1509 m) on Gunung Kanino (01°17′S, 120°08′E) on 11 May, 1975; 2 females ex male P. topapuensis (AMNH 226932) collected by G.G. Musser at 1000 m at Tomado, Danau Lindu (1°19′S, 120°03′E) on 15 August, 1973; 2 females ex male P. topapuensis (AMNH 223532) collected by G.G. Musser at 4800 ft (1463 m) on Gunung Kanino (1°17′S, 120°08′E) in November 1973. All localities are in the central core of Sulawesi (Propinsi Sulawesi Tengah). Paratypes are deposited in AMNH, BMNH, LAD, and USNM.

Distribution

Hoplopleura topapuensis is known only from Prosciurillus topapuensis, which is restricted to middle elevations and mountains in the central core of Sulawesi (see fig. 11 and table 4). It has been collected from squirrels trapped at elevations between 1000 m and 1463 m.

Etymology

Hoplopleura topapuensis has been named for the specific epithet of its host.

Diagnosis

Hoplopleura topapuensis can be distinguished from all other species of Hoplopleura using a combination of the following characters: (1) the presence of three dorsal abdominal plates posteriorly in the male; (2) the shape of the thoracic sternal plate; (3) the shape and length of the apical paratergal setae in both sexes; (4) the shape, proportions, and setation of the male and female genitalia. This species is morphologically similar to Hoplopleura murinus n. sp., a parasite of Prosciurillus murinus, which is also described in this paper. These two species of Hoplopleura can be distinguished using the following characters. Males: (1) five dorsal abdominal plates posteriorly in H. murinus n. sp. compared to three plates in H. topapuensis; (2) one short apical seta and one seta of intermediate length on paratergal plate III in H. murinus n. sp. compared to two fairly long apical setae on this plate in H. topapuensis; (3) two apical setae of intermediate length on paratergal plate VI in H. murinus n. sp. compared to one short apical seta and one fairly long apical seta on this plate in H. topapuensis; (4) a distinct lateral protuberance on each side of the pseudopenis in H. murinus n. sp.—this is absent in H. topapuensis, which has finely crenulated lateral margins on each side of the pseudopenis; (5) the smaller size of H. murinus (range, 0.62–0.74 mm) compared to H. topapuensis (range, 0.83–0.99 mm). Females: (1) one row of 4 DCAS immediately preceding the dorsal abdominal plates in H. murinus n. sp. compared to 9–10 DCAS in this position in H. topapuensis; (2) 3–4 DLAS and no VLAS in H. murinus n. sp. compared to 10–20 DLAS and 10–20 VLAS in H. topapuensis; (3) gonopod VIII with four setae in H. murinus n. sp. but with three setae in H. topapuensis; (4) the smaller size of H. murinus n. sp. (range, 0.85–1.03 mm) compared to H. topapuensis (range, 1.04–1.39 mm).

Description

Male (fig. 50A–D). Length of holotype 0.99 mm (mean for series 0.91; range 0.83–0.99, N  =  2). Head, thorax, and abdomen well sclerotized.

Fig. 55

Hoplopleura abstrusus, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head. Longer than wide with broadly rounded anterior apex; 2 SuHS, 3 DMHS, 1 DAnCHS, 1 SpAtHS, 2–3 AnMHS, and 1 VPHS on each side; DPHS fairly long, extending to mesothoracic spiracle, with 1 DAcHS medial to DPHS. Antennae. 5-segmented with basal segment much wider than second segment, wider than long.

Thorax. Broader than long; thoracic sternal plate (fig. 50B) with broadly rounded anterior apex and tapering, broadly rounded posterior apex; mesothoracic spiracle moderate in size (0.017 mm in diameter); DPTS moderate in length (0.135 mm) almost extending to anterior region of paratergal plate III; 1 DMsS anteromedial to DPTS. Legs. Fore and mid-coxae subtriangular; forelegs small each with narrow acuminate claw; hindlegs robust each with broad acuminate claw; midlegs intermediate in size between fore and hind legs.

Abdomen. Wider than thorax; one plate per segment dorsally on segments 7–9; one broad plate per segment ventrally on segments 1 and 2; two plates per segment ventrally on segments 3–7; segment 3 with one broad and one narrow plate ventrally; first row of DCAS with two setae, second and third rows each with 4 DCAS, and rows 4–7 each with 8–10 DCAS, followed by two rows of TeAS each with 6–8 setae and by one row of 2–3 TeAS; 1 DLAS on each of segments 7 and 8; first ventral plate without setae; ventral plates 2–12 each with 4–8 StAS; ventral plates 2 and 3 each articulating with corresponding paratergal plates. Paratergal plates (fig. 50C) present on segments 1–8: plate II with one fairly long apical seta and one of intermediate length; plate III with two apical setae of intermediate length; plates IV–VI each with one short apical seta and one of intermediate length; plates VII and VIII each with two long apical setae; all plates subtriangular; plates II–VI each with both apical angles produced into points; plates III–VII each with moderate size spiracle.

Genitalia (fig. 50D). Aedeagal basal apodeme about as long as parameres; parameres curved and tapering posteriorly; pseudopenis short, barely extending beyond apices of parameres; lateral margins of pseudopenis crenulated.

Female (fig. 51A–D). Length of allotype 1.29 mm (mean for series 1.19; range 1.04–1.39; N  =  15).

Fig. 56

Hoplopleura heinrichi, male. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head, thorax, and legs. As in male unless indicated otherwise. 4 DMHS on each side of head.

Abdomen. Wider than thorax; three plates per segment dorsally on segments 4–6; two plates per segment dorsally on segments 7 and 8; one broad plate ventrally on each of segments 1 and 2; two broad plates ventrally on segment 3; three plates per segment ventrally on segments 4–7; first row of DCAS with two setae, second and third rows each with 4 DCAS, row 4 with 8–10 DCAS, followed by 13 rows of TeAS each with 6–9 setae; first ventral plate lacking setae; ventral plates 2–16 each with 6–9 StAS; ventral plates 2 and 3 each articulating with corresponding paratergal plates; rows of 1–2 DLAS and VLAS on segments 4–8. Paratergal plates (fig. 51C) as in male except both apical setae on plate III fairly short; plates II–VI subtriangular.

Genitalia (fig. 51D). Subgenital plate with deep lateral indentation on each side; two long lateral setae on each anterior arm of subgenital plate; gonopod VIII with two short medial apical setae and one lateral apical seta of intermediate length; gonopod IX with one stout seta; vulvar fimbriae distinct.

Hoplopleura murinus, new species

Holotype

Male and allotype female ex female Prosciurillus murinus (AMNH 226073; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by G.G. Musser at 450 ft at Malakosa, Kuala Navusu (0°58′S, 120°27′E; see gazetteer and fig. 30), Propinsi Sulawesi Tengah, Indonesia on 5 October, 1975. The holotype is deposited in USNM.

Referred Specimens

An additional seven males and 21 females from the same host individual as the holotype and allotype; one female ex female P. murinus (USNM 216794) collected by H.C. Raven at 0–100 m at Teteamoet (1°40′N, 125°05′E), North Sulawesi on 28 January 1916; three males, six females ex female P. murinus (AMNH 224596) collected by G.G. Musser at 2700 ft at Sungai Sadaunta (1°23′S, 119°58′E), central Sulawesi on 26 September, 1974.

Distribution

Hoplopleura murinus has been collected from voucher hosts of Prosciurillus murinus from both the northern peninsula and central core of Sulawesi. The squirrel host is found in lowland and montane forest habitats throughout Sulawesi (see fig. 11 and table 4).

Etymology

This species is named for the specific epithet of its host.

Diagnosis

Hoplopleura murinus can be distinguished from all other species of Hoplopleura using a combination of the following characters: (1) the presence of five dorsal abdominal plates situated posteriorly in the male; (2) the shape of the thoracic sternal plate in both sexes; (3) the shape of the paratergal plates and the lengths of the apical paratergal setae in both sexes; (4) the shape, setation, and proportions of the male and female genitalia. Hoplopleura murinus appears to be most similar to Hoplopleura topapuensis; key differences between these two new anopluran taxa are discussed in the descriptive section on H. topapuensis.

Description

Male (fig. 52A–D). Length of holotype 0.74 mm (mean for series 0.69; range 0.62–0.76; N  =  11). Head, thorax, and abdomen well sclerotized.

Fig. 57

Hoplopleura heinrichi, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head. Longer than wide with broadly rounded anterior apex; 2 SuHS, 4 DMHS, 1 DAnCHS, 1 DPoCHS, 1 SpAtHS, 2 DPaHS, 1 VPHS, and 3–4 AnMHS on each side; DPHS fairly long with 1 DAcHS medial to DPHS. Antennae. 5-segmented with basal segment wider than second segment, wider than long.

Thorax. Broader than long; thoracic sternal plate (fig. 52B) tapering to blunt anterior apex and to more acute posterior apex; mesothoracic spiracle fairly small (0.014 mm in diameter); DPTS moderate in length (0.105 mm) extending to anterior region of third paratergal plate; one small DMsS medial to spiracle. Legs. Hind coxae with spurlike posterior projection; fore and mid coxae subtriangular, each with three small setae; forelegs fairly small each with narrow acuminate claw; hindlegs robust, each with large acuminate claw; midlegs intermediate in size between fore and hindlegs.

Abdomen. Wider than thorax; one broad plate per segment dorsally on segments 5–8; one broad plate per segment ventrally on plates 1–3; two narrow plates per segment ventrally on segments 4–7; five rows of DCAS dorsally—row 1 with 2 DCAS, rows 2 and 3 each with 4–5 DCAS, and rows 4 and 5 each with 6–8 DCAS, followed by four rows of TeAS with 5, 5, 5, and 1 setae, respectively; first ventral plate lacking setae; second ventral plate with 8 StAS; third ventral plate with 6 StAS including two large lateral setae on each side (three on one side in holotype); ventral plates 2 and 3 each articulating with corresponding paratergal plate; ventral plates 4–11 each with 5–10 StAS; some dorsal and ventral abdominal setae dagger-shaped. Paratergal plates (fig. 52C) present on segments 1–8: plate I without setae; plate II with one fairly long apical seta and one seta of intermediate length; plates III–V each with one short apical seta and one seta of intermediate length; plate VI with two apical setae of intermediate length; plates VII and VIII each with two long apical setae; plates II–VII subtriangular; plates II–VI each with both apical angles produced into points; plates III–VII each with moderate size spiracle.

Genitalia (fig. 52D). Aedeagal basal apodeme about same length as parameres; parameres curved with differential sclerotization; pseudopenis barely extending beyond apices of parameres, with small lateral protuberance on each side.

Female (fig. 53A–D). Length of allotype 0.94 mm (mean for series 0.94; range 0.85–1.03; N  =  27).

Fig. 58

Hoplopleura ileile, female. A, dorsoventral view; B, thoracic sternal plate; C, paratergal plates; D, genitalia.

Head, thorax, and legs. As in male unless indicated otherwise. DPTS length 0.113 mm. Thoracic sternal plate (fig. 53B) similar in both sexes but anterior apex more acute in most female specimens.

Abdomen. Wider than thorax; three narrow plates per segment dorsally on segments IV–VIII; 1 broad plate ventrally on each of segments 1–3; three narrow plates per segment ventrally on segments IV–VII; first row of dorsal setae with 2 DCAS, second and third dorsal rows each with 4 DCAS, followed by 15 rows of 5–9 TeAS; few DLAS present; first ventral plate lacking setae, second ventral plate with 8 StAS, third ventral plate with 9 StAS (including two longer, robust setae on each side), and following ventral plates each with 7–10 StAS; ventral plates 2 and 3 each articulating with corresponding paratergal plate; some dorsal and ventral abdominal setae dagger-shaped. Paratergal plates (fig. 53C) present on segments 1–8: plate I lacking setae; plates II and IV–VI each with one short apical seta and one seta of intermediate length; plate III with two apical setae of intermediate length; plates VII and VIII each with two long apical setae; plates II–VIII subtriangular; plates III–VII each with moderate size spiracle.

Genitalia (fig. 53D). Subgenital plate with deep lateral indentation on each side; two long setae on each anterior arm of subgenital plate, and four short central setae between these; gonopod VIII with three short apical setae and one subapical seta of intermediate length; gonopod IX with one stout seta; vulvar fimbriae distinct.

Remarks

Like its squirrel host, Prosciurillus murinus, this louse is smaller in body size than its Sulawesian congeners that parasitize other species of Sulawesian squirrels.

Hoplopleura abstrusus, new species

Holotype

Male ex male Prosciurillus abstrusus (AMNH 101359; Rodentia: Sciuridae: Nannosciurinae, Nannosciurini, Hyosciurina) collected by G. Heinrich at 2000 m at Tanke Salokko (3°40′S, 121°13′E; see gazetteer and fig. 30), Pegunungan Mekongga on the southeastern peninsula of Sulawesi (Propinsi Sulawesi Tenggara), Indonesia on 18 December, 1931. The holotype is deposited in USNM.

Referred Specimens

The following additional specimens, all collected by G. Heinrich on various dates during December 1931 from the same host species at the same location as the holotype: an additional male, four females, one nymph from the same host individual as the holotype; one nymph ex male P. abstrusus (AMNH 101349) at 2000 m; three females ex male P. abstrusus (AMNH 101350) at 1500 m; two females, three nymphs ex male P. abstrusus (AMNH 101352) at 2000 m; two females ex female P. abstrusus (AMNH 101353) at 2000 m; one male, two females (including allotype), one nymph ex female P. abstrusus (AMNH 101354) at 2000 m; four females ex male P. abstrusus (AMNH 101355) at 2000 m; one male ex male P. abstrusus (AMNH 101358) at 2000 m; two males, five females, three nymphs ex male P. abstrusus (AMNH 101360) at 2000 m; two females, one nymph ex male P. abstrusus (AMNH 101361) at 2000 m; one male, three females, one nymph ex sex unknown P. abstrusus (AMNH 101362) collected at 2000 m. Paratypes are deposited in AMNH, BMNH, LAD, and USNM.

Distribution

All collections of Hoplopleura abstrusus are from Prosciurillus abstrusus collected from Tanke Salokko, Pegunungan Mekongga, on the southeastern peninsula of Sulawesi at 1500 m or 2000 m. The tree squirrel is endemic to this mountain range (see fig. 11 and table 4).

Etymology

The specific epithet of the host has been used to name this louse.

Diagnosis

Hoplopleura abstrusus can be distinguished from all other species of Hoplopleura using a combination of the following characters: (1) four rows of dorsal abdominal setae followed by five dorsal abdominal plates in the male; (2) characteristically shorter, stout setae in some rows of dorsal abdominal setae; (3) morphology of the male genitalia, especially the pseudopenis which has lateral projections, and also extends well beyond the apices of the parameres; (4) four rows of DCAS followed by 13 dorsal abdominal plates in the female; (5) setal lengths on gonopod VIII in the female; (6) shape of the subgenital plates in both sexes; (7) shape and setation of the paratergal plates in both sexes.

Description

Male (fig. 54A–D). Length of holotype 0.93 mm (mean for series 0.91, range 0.87–0.94, N  =  7). Head and thorax well sclerotized.

Fig. 59

Maximum parsimony majority rule consensus tree showing phylogenetic relationships among species of Hoplopleura from rodent hosts based on 43 morphological characters. Maximum parsimony bootstrap support values and Bayesian posterior probabilities are indicated above the nodes and Bremer support values are given below the nodes. Species of sucking lice parasitizing endemic Sulawesi squirrels form a monophyletic group (indicated in the gray box).

Head. Longer than wide with broadly rounded, anterior apex; 2 SuHS, 4 DMHS, 1 DAnCHS, 1 DPoCHS, 3 SpAtHS, 2–3 DAnMHS, and 1 OrS on each side. DPHS short, barely extending beyond posterior margin of head with 1 DAcHS medial to DPHS. Antenna 5-segmented with basal segment wider than second segment, much wider than long; second segment elongate.

Thorax. Broader than long; thoracic sternal plate (fig. 54B) blunt anteriorly and tapering to rounded posterior apex; mesothoracic spiracle small (0.015 mm in diameter) with one long DMsS and one DPTS of moderate length (0.11 mm) medial to spiracle. Legs. Forelegs and midlegs small each with narrow, acuminate claw; hindlegs and hind claws robust.

Abdomen. Wider than thorax; five rows of DLAS/DCAS anteriorly: rows 1 and 2 each with two setae, rows 3 and 4 each with four setae, row 5 with 8–10 setae; five dorsal plates posterior to DLAS/DCAS rows: plates 1–4 each with 7–12 TeAS, plate 5 without setae; 1–2 DLAS on segments 4–6; some dorsal abdominal setae characteristically peg-like or dagger-like; 11 ventral abdominal plates: plate 1 small and lacking setae, plates 2–11 each with 6–8 StAS, plates 2 and 3 each extending laterally to articulate with corresponding paratergal plate as characteristic of genus, plate 3 with 2 elongate lateral StAS on each side; 1 VLAS on each of segments 3–7 or 3–8. Paratergal plates (fig. 54C) present on segments 1–8: plate I lacking setae; plates II and III each with 2 apical PrS of intermediate length; plates IV–VI each with 1 short apical PrS and 1 PrS of intermediate length; plates VII and VIII each with 2 long apical PrS; plates II–VI subtriangular and with both apices developed into points; plates III–VII each with moderate-size spiracle.

Genitalia (fig. 54D). Subgenital plate with small lateral ridge and four long anterior setae on each side (as shown in fig. 54A); aedeagal basal apodeme almost twice as long as parameres; parameres curved and with sinuous medial margins; pseudopenis very long, extending well beyond apices of parameres, with small protuberance on each lateral margin proximal to apices of parameres.

Female (fig. 55A–D). Length of allotype 1.14 mm (mean for series 1.16, range 0.95–1.40, N  =  27).

Fig. 60

Valley of Danau Lindu, 1000 m, in the northern highlands of the western mountain block of Sulawesi's central core. Part of Tomado village is in the foreground on the shore of a small cove. Tropical lowland evergreen rain forest is at lake level and mantles hillsides of the closer ridges. Upper slopes and summits in the background are clothed in montane forest formations. The large, red tree squirrel Rubrisciurus rubriventer lives in intact forest near the lake and in forests on the ridges to about 1500 m. Montane forests on the upper slopes and summits of the higher ridges (Gunung Nokilalaki is the farthest ridge seen in the background), support one ground squirrel, Hyosciurus heinrichi, which abuts the range of the other ground squirrel H. ileile at 1400–1500 m, and that species, while uncommon, occurs throughout the region at lower altitudes. The tree squirrels Prosciurillus topapuensis and P. murinus inhabit all old-growth habitats, from lakeside to tops of the highest ridges. Photographed in 1976.

Head, thorax, and legs. As in male.

Abdomen. Wider than thorax; four rows of setae dorsally with 2, 4, 4, and 8 setae, respectively, followed by 13 dorsal plates each with 5–10 TeAS; plate 13 broad; 1–2 DLAS on each of segments 3–7, 4–7, or 3–8; 17 plates (excluding subgenital plate) ventrally: plate 1 small and lacking setae, plates 2–17 each with 5–8 StAS, plates 2 and 3 each articulating laterally with corresponding paratergal plate as characteristic of genus, plate 3 with two enlarged lateral StAS on each side; 1–2 VLAS present on each of segments 3–7, or 4–7; some TeAS, DLAS, StAS, and VLAS dagger shaped. Paratergal plates (fig. 55C) with apical PrS as in male except for one elongate apical PrS on plate II; plates II–VIII subtriangular; plates II–VII each with both apices developed into points; plates III–VII each with moderate-size spiracle.

Genitalia (fig. 55D). Subgenital plate with distal ends curved posteriorly, and with central posterior projection; one small seta on each side of midline on plate and immediately posterior to plate; gonopod VIII with three apical, posterior setae of short to intermediate length each borne on small lobe; gonopod IX with one robust seta of intermediate length; vulvar fimbriae indistinct.

Remarks

The very long pseudopenis of the male of Hoplopleura abstrusus clearly distinguishes this species from all other species of Hoplopleura that parasitize Indomalayan squirrels.

Hoplopleura heinrichi, new species

Holotype

Male and allotype female ex male Hyosciurus heinrichi (AMNH 225477; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by G.G. Musser at 7500 ft (2287 m) on Gunung Nokilalaki (1°16′S, 120°10′E; see gazetteer and fig. 35), Propinsi Sulawesi Tengah, Indonesia on 21 March, 1975. The holotype is deposited in USNM.

Referred Specimens

An additional female specimen from the same pelt as the holotype and allotype; one female ex female Hyosciurus heinrichi (AMNH 225486) collected by G.G. Musser at 5100 ft (1555 m) on Gunung Kanino (1°17′S, 120°08′E), central Sulawesi on 13 May, 1975; one female ex sex unknown Hyosciurus heinrichi (AMNH 101309) collected by G. Heinrich at 2200 m on Pegunungan Latimojong (3°31′S, 119°56′E), in the central core of Sulawesi on 10 June, 1930; one female ex female Hyosciurus heinrichi (BM 40.650 No. 7a) collected by W.J.C. Frost at 4200 ft on “Molengraff Range [ =  Pegunungan Takolekaju, see gazetteer] Mid. Celebes” in December, 1938; one male ex female Hyosciurus heinrichi (BM 40.691b) collected by W.J.C. Frost (date and elevation not given) at “Talamanti [ =  Tamalanti, see gazetteer], W. Celebes”; one male, one female ex male Hyosciurus heinrichi (BM 40.644 No. 10a) collected by W.J.C. Frost (date and elevation not given) on “Molengraff Range [ =  Pegunungan Takolekaju], Mid. Celebes.” Paratypes are deposited in AMNH, BMNH, LAD, and USNM.

Distribution

Hoplopleura heinrichi has been recorded only from Hyosciurus heinrichi, which is endemic to the western mountain block in the central core of Sulawesi (see fig. 35 and table 4).

Etymology

The specific epithet of the host has been used to name Hoplopleura heinrichi.

Diagnosis

Hoplopleura heinrichi can be distinguished from all other species of Hoplopleura using the following combination of characters: (1) the shape of the thoracic sternal plate; (2) the shape and proportions of the male genitalia; (3) the shape and setation of the female genitalia; (4) the shape and setation of the paratergal plates (one long apical seta and one seta of intermediate length on plate II in both sexes, two apical setae of intermediate length on plates III–VI, and two long apical setae on plates VII and VII in females; both apical setae are progressively longer on plates III–VII in males).

Description

Male (fig. 56A–D). Length of holotype 1.01 mm (mean for series 1.02; range 1.01–1.05; N  =  3). Head, thorax, and abdomen well sclerotized.

Head. Longer than wide with broadly rounded anterior apex; 2 SuHS, 4 DMHS, 1 DAnCHS, 1 tiny DPoCHS, 1 SpAtHS, 1 VPHS, 1 OrS, 2 ApHS, and 3–7 AnMHS on each side; DPHS long, extending to base of DPTS, with one small DAcHS medial to DPHS. Antenna 5-segmented with basal segment much larger than second segment, about as wide as long.

Thorax. Broader than long; thoracic sternal plate (fig. 56B) with broadly rounded lateral, anterior, and posterior apices; mesothoracic spiracle moderate in size (0.022 mm in diameter) with one small DMsS medial to spiracle; DPTS (0.141 mm long) extending beyond anterior attachment of paratergal plate II. Legs. Mid-coxae subtriangular; forelegs small, each with narrow acuminate claw; hindlegs robust, each with large, relatively narrow, acuminate claw; midlegs (missing except for coxa on one side of holotype) intermediate in size between fore and hindlegs.

Abdomen. Wider than thorax; one plate per segment dorsally on segments 3–8; two plates per segment ventrally on segments 4–6; first row of dorsal setae with 2 DCAS, second and third rows each with 4 DCAS, followed by 6–10 TeAS on plates 1–5; 1 DLAS on each of segments 3–7; some lateral tergal setae and DLAS thickened; first ventral plate without setae; second and third ventral plates each with 8 StAS (including two long lateral robust setae on each side on third plate) and partly extending to articulate with corresponding paratergal plates; ventral plates 4–10 each with 6–8 StAS; 1 VLAS on each of segments 3–7. Paratergal plates (fig. 56C) present on segments 1–8: plate I without setae; plates II–VIII each with two long apical setae; plates II–IV subtriangular; plates V and VI also subtriangular except for squarish anterior borders; both apical angles of plates II–VI produced into points; plates III–VII each with moderate-size spiracle.

Genitalia (fig. 56D). Aedeagal basal apodeme slightly longer than parameres; parameres curved and tapering apically; pseudopenis extending beyond apices of parameres.

Female (fig. 57A–D). Length of allotype 1.33 mm (mean for series 1.34, range 1.20–1.44, N  =  6).

Head, thorax, and legs. As in male unless indicated otherwise. 1–2 DAnHS distinct on each side. Thoracic sternal plate (fig. 57B) more elongate than in male and with less distinct lateral apices.

Abdomen. Wider than thorax; one broad plate ventrally on each of segments 1–3; three narrow plates ventrally on each of segments 4–7; one plate dorsally on each of segments 3 and 8; three narrow plates dorsally on each of segments 4–7; first ventral plate without setae, second ventral plate with 8 StAS, third ventral plate with 7 StAS (including two lateral robust setae on each side), and ventral plates 4–15 each with 6–9 StAS; 2 DCAS in first row of dorsal setae, 4 DCAS in each of dorsal rows 2 and 3, followed by 4–9 TeAS on each dorsal plate; few VLAS and DLAS present; some abdominal setae thickened or dagger-shaped. Paratergal plates (fig. 57C) as in male but with both apical setae on plates V and VI of intermediate length and with setae on plate VII shorter than in male.

Genitalia (fig. 57D). Subgenital plate with deep lateral indentation on each side, lightly sclerotized posteriorly; two long setae attached to each anterior arm of subgenital plate and four smaller central setae between these; gonopod VIII with three setae (two medial setae of intermediate length and one longer and thicker lateral seta); gonopod IX with one long stout seta; vulvar fimbriae evident.

Remarks

Hoplopleura heinrichi is distinct from the new species Hoplopleura ileile (see below), a pattern concordant with the presence of two distinctive species within Hyosciurus.

Hoplopleura ileile, new species

Holotype

Female ex female Hyosciurus ileile (AMNH 224620; Rodentia, Sciuridae, Nannosciurinae, Nannosciurini, Hyosciurina) collected by G.G. Musser at 3150 ft (960 m) at Sungai Sadaunta (1°23′S, 119°58′E; see gazetteer and fig. 35), Propinsi Sulawesi Tengah, Indonesia on 1 November 1974. The holotype is deposited in USNM.

Referred Specimens

The following specimens are all from Hyosciurus ileile hosts collected in the central core of Sulawesi by G.G., Musser: an additional two nymphs from the same individual as the holotype; two females ex male H. ileile (AMNH 224618) at 2900 ft (884 m) also at Sungai Sadaunta on 21 October 1974; one female ex female H. ileile (AMNH 226499) at 1100 ft (335 m) at Tolai, Sungai Tolewonu (1°04′S, 120°27′E) on 31 January 1976; four nymphs ex male H. ileile (AMNH 223540) at 4800 ft (1463 m) on Gunung Kanino (1°17′S, 120°08′E) on 20 November 1973. Paratypes are deposited in BMNH and LAD.

Distribution

Hoplopleura ileile is known from voucher hosts collected at only three localities in the northern portion of Sulawesi's central core. Samples of the ground squirrel are from the northern part of the west-central region in the central core and one locality on the northern peninsula (see fig. 35 and table 4).

Etymology

Hoplopleura ileile has been named for the specific epithet of its host.

Diagnosis

The female of Hoplopleura ileile can be distinguished from all other species of Hoplopleura by a combination of the following characters: (1) the arrangement of the dorsal and ventral abdominal plates and the rows of DCAS and VCAS between these plates; (2) the shape of the thoracic sternal plate; (3) the shape and setation of the paratergal plates; and (4) the shape and setation of the subgenital plate. The female of Hoplopleura ileile differs from the female of Hoplopleura heinrichi in several characters including the following: (1) the shape of the thoracic sternal plate, which is elongate in Hoplopleura heinrichi (fig. 57B) but more diamond-shaped with a blunt anterior apex and with distinct lateral apices in Hoplopleura ileile (fig. 58B); (2) the shape and setation of the paratergal plates, especially the longer apical setae on plate II of Hoplopleura heinrichi (figs. 57C and 58C); (3) the significant reduction in the number and width of the dorsal and ventral abdominal plates in Hoplopleura ileile when compared to Hoplopleura heinrichi; (4) the presence of rows of DCAS and VCAS between rows of TeAS and StAS in Hoplopleura ileile but not in Hoplopleura heinrichi (except for a few long setae situated anteriorly on the venter of Hoplopleura heinrichi); (5) the larger number of dagger-shaped abdominal setae in Hoplopleura heinrichi; (6) the difference in the shapes of the subgenital plates, especially the deeper lateral indentations in Hoplopleura ileile.

Description

Female (fig. 58A–D). Length of holotype 1.05 mm (mean for series 1.07, range 1.05–1.09, N  =  4). Head, thorax, and abdomen fairly well sclerotized.

Head. Longer than wide with broadly rounded anterior apex; 2 SuHS, 4 DMHS (displaced medially in some specimens as in fig. 58A), 1 DAnCHS, 1 DPoCHS, 1 SpAtHS, 1 DPaHS, 2DAnHS, 1 ApHS, 1–2 AnMHS, 1–2 OrS, and 1 VPHS on each side; DPHS moderate in length, just extending to level of thoracic spiracle with 1 DAcHS medial to DPHS. Antenna 5-segmented with basal segment wider than second segment, about as wide as long.

Thorax. Broader than long; thoracic sternal plate (fig. 58B) diamond shaped but with blunt anterior apex, moderately rounded posterior apex, and bifid lateral apices; mesothoracic spiracle moderate in size (0.020 mm in diameter) with 1 DMsS medial to spiracle; DPTS moderate in length (0.125 mm in paratypes, broken in holotype), extending to paratergal plate II. Legs. Forelegs small with narrow acuminate claw; midlegs and hindlegs progressively larger than forelegs with proportionately larger acuminate claws; mid coxae subtriangular.

Abdomen. Wider than thorax with one plate ventrally on each of segments 1–3 and 5–6; one to two narrow plates dorsally on segment 3 and two narrow plates dorsally on segments 4–6; rows of VCAS between StAS; rows of TeAS between pairs of dorsal plates as in figure 58A; first ventral plate without setae, second ventral plate broad, articulating with corresponding paratergal plate, and with 8–10 StAS, including 3–4 (usually three) clustered laterally on each side; third ventral plate also articulating with corresponding paratergal plate but with 7 StAS (including two long, lateral setae on each side); remaining two ventral plates with 4–5 and 5–7 StAS, respectively; rows of 5–8 VCAS present between ventral plates as shown in figure 58A; first row of DCAS with two setae, second and third rows each with 4 DCAS, and other rows with 5–8 DCAS between dorsal plates as shown in figure 57A; 2–8 TeAS on each dorsal plate; few VLAS and DLAS present; some posterior VLAS and DLAS dagger shaped. Paratergal plates (fig. 58C) present on segments 1–8: plate I small and lacking setae; plate II with two short apical setae of subequal length; plates III–VI each with two apical setae of intermediate length; plates VII and VIII each with two long apical setae; plates II–VIII subtriangular; plates III–VII each with moderate-size spiracle.

Genitalia (fig. 58D). Subgenital plate with deep lateral indentation on each side, lightly sclerotized posteriorly; two long setae on each anterior arm of subgenital plate, and 3–4 small central setae between these; gonopod VIII with three setae with lateral seta longer than medial and central setae; gonopod IX with one long stout seta.

Remarks

The presence of two species of sucking lice on the two host species, Hyosciurus heinrichi and Hyosciurus ileile, augments the morphological and morphometric data that provide support for the phenetic and taxonomic separation of the hosts. As a group, lice associated with mammals typically phyletically track their hosts (Kim, 1985, 1988; Lyal, 1986, 1987; Grimaldi and Engel, 2005; Light and Hafner, 2007; Smith et al., 2008) so that host speciation often (in about 80% of known cases) also results in louse speciation (Fahrenholz's Rule). Because Hoplopleura heinrichi and Hoplopleura ileile are distinct taxa and provide important inferences for the taxonomy of their hosts, we felt that both lice should be described in this paper despite the availability of only females and nymphs for the latter species. Nevertheless, two third-instar nymphs of Hoplopleura ileile that were preserved just prior to molting to adult males were available and it was from these pharate males (clearly visible beneath the nymphal cuticle) that we assessed male characters for cladistic analyses.

With the species of Hoplopleura from the Sulawesi squirrels named and described, the next step is to discuss them in three contexts. First, we provide results of our analysis of the phylogenetic relationships among the Sulawesi louse species and other species of Hoplopleura on Indomalayan squirrels. Second, we place the Sulawesi Hoplopleura within a portrayal of global sciurid-Anoplura associations. Finally, we use the information presented within the frameworks of the first and second contexts to describe zoogeographic patterns formed by the genera of Anoplura infesting Indomalayan squirrel faunas. The following three sections cover these subjects.