A large collection of mollusks was recently acquired by the Museu de Zoologia da Universidade de São Paulo (Brazil) from a commercial company. In this collection, the specimens of the family Streptaxidae from Brazil are both diverse and relatively abundant and are examined here. Herein are reported new records of 11 species, greatly extending the geographical range of the following: Rectartemon depressus (Heynemann, 1868), R. iguapensis (Pilsbry, 1930), R. piquetensis (Pilsbry, 1930) and Streptartemon extraneus (Haas, 1955). Additionally, two new species are described: Streptaxis leirae sp. nov. and Streptaxis megahelix sp. nov.
1 Introduction
A large collection of mollusks was recently acquired by the Museu de Zoologia da Universidade de São Paulo (MZSP; São Paulo, Brazil), comprising circa 10,000 lots from all regions of the globe. As this collection belonged to the commercial company Femorale, the specimens are usually in very good state of preservation and include detailed data on the collection localities (albeit not precise coordinates) and sometimes habitat. Despite most of the collection being of marine mollusks, a good portion is devoted to land snails. Among these, the sample of the family Streptaxidae from Brazil deserves further attention due to the diversity of species present and relative abundance of specimens (when compared to other families in the acquired collection). This sample counts with 37 specimens from 11 unique localities in Brazil, mostly belonging to the Atlantic forest biome, which is in particularly urgent need of better documentation of its invertebrate biodiversity.
Streptaxids are carnivorous pulmonate land snails belonging to the Stylommatophora, distributed mainly in South America, Africa and tropical Asia (Rowson et al., 2010). The family's fossil record goes back to the Late Cretaceous of Europe and a Mesozoic Gondwanan origin has been proposed, with later radiation events (Zilch, 1960; Rowson et al., 2010). The most thorough works dealing with the taxonomy of South American streptaxids at the species level are Tryon (1885) and Gude (1902), while for Brazil there are a handful of species lists, such as Morretes (1949), Salgado & Coelho (2003) and Simone (2006), the latter being the most complete and the only one illustrated. The 52 streptaxid species known in Brazil are presently distributed into six genera (Simone, 2006; Birckolz et al., 2016): Hypselartemon Wenz, 1947, Martinella Jousseaume, 1887, Rectartemon Baker, 1925, Sairostoma Haas, 1938, Streptartemon Kobelt, 1905, and Streptaxis Gray, 1837.
In the present work, new occurrences of streptaxids are reported, significantly extending the known geographical ranges of these species within Brazil. In addition, two new species of Streptaxis are described.
Acronyms of depositories
ANSP
Academy of Natural Sciences of Drexel University (Philadelphia, USA)
FMNH
Field Museum of Natural History (Chicago, USA)
MZSP
Museu de Zoologia da Universidade de São Paulo (São Paulo, Brazil)
ZMB
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung (formerly “Zoologisches Museum Berlin”; Berlin, Germany).
2 Material and Methods
The lots acquired from Femorale represent haphazard collections with a clear commercial intent. Nevertheless, data on Brazilian terrestrial gastropods is so scarce that even such collections can greatly improve current knowledge. The material, comprising only empty shells, is deposited in the malacological collection of MZSP. The streptaxid specimens (n = 37) were collected from 2007 to 2015 in 11 different localities, most of them belonging to eastern Brazilian states (Table 1) and representing the Atlantic Forest biome.
Table 1.
List of all Streptaxidae species found in the new collection acquired by the MZSP, with the studied material and the localities of their occurrence. Abbreviations: s = shell(s); HOL, holotype; PAR, paratype(s). Brazilian states: BA = Bahia, ES = Espírito Santo, MG = Minas Gerais, R.T = Rio de Janeiro, RN = Rio Grande do Norte.
All streptaxid taxa found in the present collection and their primary data are listed in Table 1, and those species for which geographical ranges are extended are figured and further discussed in the Systematic section below. Likewise, the new species descriptions can be found below.
Identification of the material was conducted based on the original descriptions and further taxonomic literature, especially the catalogue of Simone (2006). Additional comparisons were made with material, including types, housed in MZSP and other collections (indicated below as necessary). Imaging and measurements were made with the aid of the Zeiss Axiovision SE64 Re14.8 software.
3 Systematics
Superfamily Streptaxoidea
Family Streptaxidae
Rectartemon Baker, 1925
Rectartemon depressus (Heynemann, 1868)
(Figs. 1–3)
Streptaxis depressas Heynemann, 1868: 101, pl. 4, fig. 2 [August; name and description of radula].
Streptaxis apertus Martens 1868: 180 [October; description of shell]; Pfeiffer, 1876: 491; Pfeffer, 1878: 69, figs. 9–10; Schade, 1965: 218.
Streptaxis apertus subglobosus Martens 1868: 180; Pfeiffer, 1876: 491.
Streptaxis apertus depressus Martens 1868: 180; Pfeiffer, 1876: 491; Parodiz, 1957: 64; Figueiras, 1963: 92; Fernandez & Castellanos, 1973: 272; Quintana, 1982: 103.
Streptaxis (Artemon) apertus: Tryon, 1885: 63; Gude, 1902: 229.
Streptaxis (Artemon) apertus var. depressus: Tryon, 1885: 63.
Streptaxis (Artemon) apertus var. depressa: Clessin, 1888: 165; Gude, 1902: 229.
Alcidia aperta: Bourguignat, 1889: 47.
Rectartemon apertus: Gude, 1903: 229; Zilch, 1961: 80; Salgado & Coelho, 2003: 170.
Artemon apertus: Kobelt, 1906: 43, pl. 48, figs. 10–12; Jaeckel, 1927: 137; Solem, 1956: 10, pl. 1, figs. 8–10.
Rectartemon (Rectartemon) depressus: Picoral & Thomé, 1993: 5; Picoral & Lopes-Pitoni, 1998: 117, figs. 1–8; Picoral & Thomé, 1998: 101.
Rectartemon depressus: Simone, 2006: 198, fig. 743; Lemos et al., 2012: 128, figs. 1–2.
Type locality: Unknown. The locality of Martens (1868) has been interpreted by Gude (1902) as “South Brazil”, while Pereira & Thomé (1999) indicates Morro Reuter municipality in Rio Grande do Sul state as a possible candidate.
Previously known distribution: Known from Brazil (Espírito Santo, Rio Grande do Sul, Santa Catarina and São Paulo states), Paraguay (Alto Paraná, Caaguazú, Concepción, Guairá, Itapúa, Paraguarí and San Pedro departments), Argentina (Buenos Aires [Martín García Island], Corrientes, Entre Ríos, and Missiones provinces) and Uruguay (Paysandú department) (Parodiz, 1957; Figueiras, 1963; Quintana, 1982; Simone, 2006).
New occurrence: Brazil: Minas Gerais state, Nanuque. Rio de Janeiro state. Serra de Macaé.
Remarks: This species is characterized by the comparatively deeper suture and by the presence of axial ribs on the abapical portion of the whorls (Picoral & Lopes-Pitoni, 1998). The present material closely resembles the types (ZMB/MOLL. 13729, 11 syntypes of S. depressus; ZMB/ MOLL. 57163, holotype of S. apertus). The present record slightly extends the species' distribution to the north; the records are from the border of Espírito Santo state with the states of Minas Gerais (Nanuque municipality) and Bahia.
Rectartemon iguapensis (Pilsbry, 1930)
(Figs. 4–6)
Artemon iguapensis Pilsbry, 1930: 363, pl. 32, figs. 4, 4a, 4b; Morretes, 1949: 166; Solem, 1956: 10, pl. 1, figs. 14–16.
Streptaxis iguapensis: Salgado & Coelho, 2003: 171.
Rectartemon iguapensis: Simone, 2006: 198, fig. 744; Salvador et al., 2016: table 1.
Type locality: Brazil: São Paulo state, Iguape.
Previously known distribution: Known from Bahia and São Paulo states (Simone, 2006).
New occurrence: Brazil: Rio de Janeiro state. Serra de Macaé.
Remarks: Even with a juvenile specimen, the number of whorls, relatively narrow umbilicus, conical spire and the telltale keel on the mid portion of the whorl (Pilsbry, 1930; Solem, 1956) allow the identification as R. iguapensis.
Rectartemon piquetensis (Pilsbry, 1930)
(Figs. 7–9)
Artemon intermedius piquetensis Pilsbry, 1930: 365, pl. 32, figs. 5a–b; Morretes 1949: 166.
Artemon piquetensis: Solem, 1956: 10.
Streptaxis piquetensis: Salgado & Coelho 2003: 171.
Rectartemon piquetensis: Simone, 2006: 199, fig. 746; Birckolz et al., 2016: table 1; Simone & Salvador, 2016: table 1, figs. 93–95.
Type locality: Brazil: São Paulo state, Piquete.
Previously known distribution: Known from Bahia, Minas Gerais and São Paulo states (Birckolz et al., 2016).
New occurrence: Brazil: Rio de Janeiro state. Serra de Macaé.
Remarks: In spite of the present specimens being juveniles or sub-adults, some features allow the identification as R. piquetensis, such as the relatively large size when compared to most congeners, the raised spire, and the rounded profile of the body whorl (“indistinctly subangular” sensu Pilsbry, 1930). These features compare well with the type material (holotype ANSP 47581 and paratype ANSP 71248; Simone, 2006: figs. 746A and 746B, respectively), especially to the paratype.
Streptartemon Kobelt, 1905
Streptartemon extraneus (Haas, 1955)
(Figs. 10–13)
Streptaxis (Streptartemon) extraneus Haas, 1955: 102, figs. 1–3.
Streptartemon extraneus: Salgado & Coelho, 2003: 171; Simone, 2006: 197, fig. 737.
Type locality: Brazil: Pará state, Monte Alegre, Serra Formosa (near Mulata).
Previously known distribution: Known only from type locality.
New occurrence: Brazil: Rio Grande do Norte state. Natal.
Remarks: The present specimens (Figs. 10–12) compare very well with the holotype (FMNH 52354; Haas, 1955: figs. 1–3; Simone, 2006: fig. 737), especially with its diagnostic round aperture with a single parietal tooth and the nearly flat shell profile of the last and penultimate whorl above the aperture. A single specimen, however, has the last whorl positioned closer to the columellar axis, that is, less displaced laterally (Fig. 13). It is thus reminiscent in overall shell shape to some congeners, namely, S. deformis (Férussac, 1821) and S. streptodon (Moricand, 1851), while maintaining the diagnostic characters of S. extraneus. It is presently not possible to know if this is a common conchological variation of the species or if it is an aberrant form (e.g., since the specimen is rather poorly preserved, resulting from breakage and further deformed growth). All of the present specimens were collected under bushes in a dune area, indicative of a dry sandy habitat for this species. The present record greatly extends the species' range to the east.
Figs. 1–13.
Streptaxidae species with geographical range extension. Specimens are shown at the same scale within each genus. – 1–3. Rectartemon depressus, MZSP 125447 (H = 11.7 mm, D = 18.7 mm). 4–6. Rectartemon iguapensis, MZSP 133139 (H = 9.8 mm, D = 14.8 mm). 7–9. Rectartemon piquetensis, MZSP 133139 (H = 14.2 mm, D = 21.0 mm). 10–12. Streptartemon extraneus, specimen #1, MZSP 123558 (H = 6.1 mm, D = 7.2 mm). 13. Streptartemon extraneus, specimen #2, MZSP 123558 (H = 6.6 mm, D = 6.7 mm).
Figs. 14–18.
Streptaxis leirae sp. nov. Holotype, MZSP 129247 (H = 6.8 mm. D = 13.5 mm). The scale bar (= 1 mm) refers only to the close-up image of the protoconch and first whorls.
Streptaxis Gray, 1837
Streptaxis leirae sp. nov.
(Figs. 14–18)
Type material: Holotype: MZSP 129247 (A. Bianchi col., i/2013; Figs. 14–18).
Type locality: Brazil: Bahia state. Brumado municipality, forested area near the city.
Etymology : The name refers to Leira, a fictional goddess of illusion and mist, from the Faerûnian pantheon of the Forgotten Realms campaign setting of the Dungeons & Dragons role-playing game. This epithet, thus, also alludes to the type locality, the city of Bramado, which means “misty” in Portuguese.
Distribution: Known only from the type locality.
Habitat: The specimen was collected on the forest floor, in the leaf litter, but the type of forest was not specified. This region of Bahia state represents an area of transition between biomes, where three of the Brazilian great biomes can be found: the Atlantic Forest, the Cerrado and the Caatinga.
Material analyzed: Known only from the holotype, a complete but somewhat bleached and worn empty shell.
Diagnosis: Shell discoid to lenticular; body whorl with faint angulation, with lower (abapical) portion of the whorl strongly angulated towards the umbilicus; aperture laterally elongated; “displaced” body whorl that gives the umbilicus a somewhat “bent” appearance.
Description: Shell small (D ∼ 13 mm), discoid to lenticular, with whorls slowly increasing in width. Spire low, with step-like whorls. Whorl profile strongly convex; suture well-marked. Body whorl with faint angulation, with lower (abapical) portion of the whorl strongly angulated towards the umbilicus. Protoconch (ca. 2¼ whorls) flattened, apparently smooth (although this could be due to the shell being somewhat worn); transition to teleoconch clearly marked by an axial growth mark and start of teleoconch sculpture. Teleoconch sculptured by prosocline well-marked axial ribs on upper (adapical) portion of whorls; lower (abapical) portion smooth; sculpture apparently starts to gradually fade from the beginning of the body whorl onwards, but never completely disappears; axial growth marks present in seemingly irregular intervals. Body whorl markedly bent downwards (abapically) close to aperture. Aperture D-shaped, laterally (away from columellar axis) elongated; peristome strongly reflexed; parietal callus noticeable, but thin and incompletely defined. Umbilicus narrow, deep; body whorl seems “displaced”, giving the umbilicus a somewhat bent appearance.
Dimensions: Holotype: 6¾ whorls; H = 6.8 mm; D = 13.5 mm.
Remarks: The following features allow the classification of this new species in the genus Streptaxis: (1) the overall discoid shell shape, with the whorls of the spire well delimited by a deep suture; (2) the teleoconch sculpture present only on the upper (adapical) region of the whorls; (3) the aperture shape and the aperture region being slightly bent downwards (abapically), seen in some species like S. crossei (Pfeiffer, 1867), S. dunkeri (Pfeiffer, 1845), S. lutzelburgi Weber, 1925 and S. saopaulensis Pilsbry, 1930; (4) the somewhat “displaced” body whorl, which gives the umbilicus a rather bent appearance, as seen in some species like S. dunkeri and S. lutzelburgi. Some of these features are also known from other streptaxid genera, like Sairostoma and Streptartemon, but the whole set of features is seen only in Streptaxis. Of course, the state of the knowledge of Brazilian streptaxids is still incipient, and no major revisions have been undertaken. Nevertheless, the present species is so distinct and easily diagnosable from the presently known fauna, that it warrants description as a new taxon, namely Streptaxis leirae sp. nov.
Streptaxis leirae sp. nov. can be clearly distinguished from its congeners by its discoid shell and its strongly bent umbilicus. The only vaguely similar congeners are S. discus Pfeiffer, 1851 and S. lutzelburgi; however, the former is almost perfectly planispiral (and its occurrence in Brazil remains unconfirmed; Simone, 2006), while the latter has an overall taller spire (but also displays a bent umbilicus, although to a lesser degree than in S. leirae sp. nov.). The overall shell shape of S. leirae sp. nov. is reminiscent of Sairostoma perplexum Haas, 1938, but the aperture is completely distinct: the monospecific genus Sairostoma is diagnosable by its extremely narrow sickle-shaped aperture.
Figs. 19–24.
Streptaxis megahelix sp. nov. – 19–23. Holotype, MZSP 124024 (H = 13.5 mm, D = 18.1 mm). The scale bar (= 1 mm) refers only to the close-up image of the protoconch and first whorls. 24. Paratype (fragmentary), MZSP 124024 (H = 16.0 mm, D = 15.8 mm).
Streptaxis megahelix sp. nov.
(Figs. 19–24)
Type material: MZSP 124024 (P. Conçalves col., vii/2009): holotype (Figs. 19–23) and 2 paratypes (Fig. 24).
Type locality: Brazil: Rio de Janeiro state, São Fidélis municipality, Serra do Sapateiro.
Etymology: The composite noun in apposition refers to the many-whorled shell spire of the species.
Distribution: Known only from type locality.
Habitat: The specimens were collected from the leaf litter in an area of Atlantic Forest.
Material analyzed: Types: somewhat bleached and worn empty shells, holotype complete, but paratypes fragmentary.
Diagnosis: Shell conical, with high multi-whorled spire (ca. 10 whorls); aperture narrow, sickle-shaped.
Description: Shell small (D ∼ 18 mm), conical, multiwhorled (∼10 whorls), with whorls very slowly increasing in width. Spire high, with weakly step-like whorls. Whorl profile strongly convex; suture well-marked. Body whorl rounded. Protoconch (∼2 whorls) flattened, with first ∼½ whorl smooth (although this could be due to the shell being somewhat worn), then sculptured by prosocline axial ribs that gradually increase in strength; transition to teleoconch unclear. Teleoconch sculptured by prosocline well-marked axial ribs on upper (adapical) portion of whorls; lower (abapical) portion smooth; axial growth marks present in seemingly irregular intervals. Aperture narrow, sickle-shaped; peristome markedly reflexed (except on the palatal region closest to the suture, where it is only weakly reflexed); parietal callus distinct. Umbilicus wide, deep.
Dimensions: Holotype: 10¼ whorls; H = 13.4 mm; D = 18.1 mm. Paratype #1: 9½ whorls; H = 16.0 mm; D = 15.8 mm.
Remarks: Like Streptaxis leirae sp. nov. above, the present species can be classified in the genus Streptaxis due to its conical, many-whorled shell, with the whorls strongly delimited by a deep suture, and to its teleoconch sculpture present only on the upper (adapical) region of the whorls. Moreover, the present specimens are remarkably distinct from the presently known streptaxids and thus, are described here as a new species: Streptaxis megahelix sp. nov.
Streptaxis megahelix sp. nov. is easily distinguished from most of its congeners by its conical shell and high multi-whorled spire. There is only a handful of similar species: S. cypsele (Pfeiffer, 1849), S. iheringi (Pilsbry, 1930) and S. luetzelburgi, but none achieve the same number of whorls. Streptaxis megahelix is more similar in shape to the first two of the above-mentioned species, but it has a greater number of whorls, a much broader shell, and a much narrower (and more sickle-shaped) aperture. Moreover, S. megahelix displays neither the slightly “displaced” body whorl of S. luetzelburgi nor its abapically bent apertural region.
Even in the restricted sample, it can be seen that the species show some morphological variation, with the most complete paratype (Fig. 24) displaying a higher spire, resulting in an overall narrower shell than the holotype. Nevertheless, the range of conchological variation can only be fully assessed when more specimens become available.
4 Discussion
Although a small and haphazard collection, it is surprising how much information it adds to the knowledge of Brazilian streptaxids, from several new occurrences and geographical range extensions to the description of two new species. This reinforces the message recently argued by Birckolz et al. (2016) that knowledge of Brazilian land snails remains incipient and there is still much work to be done regarding the basics of alpha taxonomy and snail biology. As terrestrial mollusks are arguably among the most endangered animals (Lydeard et al. 2004; Régnier et al. 2008), with many species becoming extinct before being described (e.g., Richling & Bouchet 2013; Salvador & Simone 2015), this knowledge cannot come too soon and any relevant piece of information is worthwhile of study and publication.
Acknowledgements
I am very grateful to Luiz R. L. Simone (MZSP) for granting access to the collection under his care; to Carlo M. Cunha (Universidade Metropolitana de Santos) for his help in procuring most of the Paraguayan, Argentinean and Uruguayan literature; to Christine Zorn (ZMB) for the information on the types of Streptaxis depressus and S. apertus; and to Dai Herbert and Francisco Borrero for the valuable comments that greatly improved this article.
