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The earliest unquestionable records of Purgatorius (Plesiadapiformes, Primates?, Mammalia) in northeastern Montana and other areas of the Western Interior of North America are of early Paleocene, specifically middle or late Puercan (Pu 2–3 Interval Zones, undifferentiated) North American Land Mammal Age (NALMA). The report of an occurrence of Purgatorius in the Late Cretaceous (Lancian NALMA) was based on an isolated, worn lower molar found in a channel filling that is now recognized as containing a time-averaged assemblage of Lancian and earliest Puercan (Pu 1 Interval Zone) fossils. Purgatorius has not been found in large samples of other local faunas of either Pu 1 or Lancian age. In contrast, Purgatorius is abundantly represented in Pu 2–3 local faunas in the northern Western Interior suggesting that it dispersed into the area during the interval between ca. 64.75 and 64.11 Ma. Fragmentary dentaries provisionally referred to Purgatorius janisae from the Garbani Channel fauna (Pu 2–3) document its lower dental formula as: 126.96.36.199. Morphology of the canine and incisor alveoli suggests a derived gradient in crown size of: I1> or = I2 ≫ I3 ≪ C. Isolated upper incisors possibly referable to P. janisae exhibit some typical plesiadapiform specializations. Morphology of the postcanine dentition of Purgatorius is what might be expected to characterize a primitive member of the Primates, but specializations of its incisors suggest P. janisae is best considered a basal member of the Plesiadapiformes sensu lato and neither a member of nor directly ancestral to the Euprimates.
It is commonly recognized that paleontological and other biological data have numerous qualitative dimensions as well as some quantitative ones; but the fact that the latter include up to 24 or more distinct spatiotemporal dimensions has not been pointed out. Paleontologists can hold these in mind simultaneously, without effort or confusion, by virtue of these dimensions' hierarchical logical arrangement. This observation may point to a useful way of conceptualizing multiple spatiotemporal dimensions in the physical sciences.
Surface prospecting methods used for identifying microvertebrate localities suitable for wet screen-washing yield highly biased samples limited to horizons containing obvious accumulations of fossil remains. The technique is restricted to areas with well-exposed strata and results in the recovery of hydrologically concentrated faunas that are not in situ. In many areas of Utah, Cretaceous strata are either exposed in cliff faces (if the sequences are sandstone dominated), or in road cuts (if the sequences are dominated by mudstones). In order to recover fossils from these kinds of exposures in either critical stratigraphic intervals or geographic areas, I have simply “blind washed” fine-grained horizons that lack little or any evidence of fossils at the surface. This method has yielded well-preserved dentitions and skeletal elements of mammals, lizards, amphibians, and other vertebrates as well as ostracodes and gastropods. This approach permits sampling throughout the entire stratigraphic thickness of formations (providing fine-grained intervals are present) including bases and tops of units. This method also permits the recovery of biostratigraphic materials in areas where outcrops are very steep or limited to road cuts. Faunas recovered from fine-grained horizons show little evidence of transport and provide a more reliable basis for paleoecologic interpretation than hydrologically concentrated fossil accumulations. Multidisciplinary approaches to nonmarine biostratigraphy that incorporate all vertebrates, invertebrates, and palynomorphs as well as “blind washing” techniques should be able to establish biostratigraphies with resolutions that rival marine biostratigraphic schemes.
A neotype has been selected for the lost type specimen of Viviparus paludinaeformis (Hall) 1845 from its type locality. In addition, the identifications and type localities of other lost non-marine molluscan fossils collected by the John C. Frémont topographic engineers expeditionary force are documented.
Although camelids, in general, are characterized by uncomplicated, conservative occlusal wear patterns in the cheek teeth, attention to details can sometimes reveal important differences among taxa. In this paper, sequential wear stages in the posterior deciduous premolars and molars are described and compared between the brachydont Miocene camelids Miolabis princetonianus and “Oxydactylus” sp., cf. “O”. longirostris and the hypsodont Miocene camelid Michenia sp. It is found that there are differences between the brachydont camelids on the one hand, and the hypsodont camelid on the other, in the overall occlusal wear patterns, the order in which the molar lophs and lophids become linked, and the relative age (wear stage) at which these connections are established. In the lower teeth, Michenia sp. shows early formation of lophids and reduction of fossettids in the DP4, M1, and M2 compared to M. princetonianus and “O.” sp., cf. “O”. longirostris. Also, the protoconid-hypoconid lophid is the last to form on the M2–3 of Michenia sp., whereas in the brachydont camelids the metaconid-entoconid lophid is the last to form. In the upper teeth, Michenia sp. again shows earlier completion of cross lophs in DP4, M1, and M2 than in M. princetonianus and “O.” sp., cf. “O”. longirostris. Also, in M1–3 the metaloph is completed prior to the completion of the protoloph and hypoloph, whereas in the brachydont camelids the protoloph and hypoloph are completed before the metaloph. Minor differences are also evident between Miolabis princetonianus and “O.” sp., cf. “O”. longirostris in the sequential changes in wear patterns. Wear patterns in some other camelid taxa are briefly compared and found to exhibit (1) features common to brachydont or hypsodont camelids, but also, (2) minor differences, of possible taxonomic use, between each other.
At least seven groups of ungulates occurred in South America during the Tertiary: Litopterna, Notoungulata, Astrapotheria, Xenungulata, Pyrotheria, Didolodontidae, and kollpaniine mioclaenid condylarths. Astrapotheria and Litopterna also occurred in Antarctica. Condylarths from North America and Europe are diverse and numerous and evolutionary relationships of South American ungulates with several of them have been suggested. A phylogenetic analysis of representatives of most living placental mammal orders, several groups of North American and European condylarths, and three groups of South American ungulates (Litopterna, Notoungulata, and Astrapotheria) is presented here. The analysis is based solely on postcranial characters. There is very limited information available about the postcranium of South American condylarths, xenungulates, and pyrotheres; therefore they are not included here. The cladogram indicates that litopterns and notoungulates are sister taxa, with the phenacodontid Meniscotherium as their closest North American relative; Astrapotheria would have shared a common ancestor with Periptychida.
A simplicidentate mammal, Hanomys malcolmi, new genus and species, is the only fossil currently known from a recently discovered, presumably Paleocene, locality near Danjiangkou, Hubei Province, China. The specimen consists of the anterior part of a skull with complete dentition and articulated lower jaw, lacking only P3. Hanomys resembles the mixodont simplicidentates Heomys and Eurymylus in dental formula and general morphology of the cheek teeth. It differs from them in a combination of characters such as a more expanded hypocone on P4–M2 and dorsoventral expansion of the anterior root of the zygomatic arch. These characters indicate that Hanomys is at the root of the clade that includes Rhombomylus and Matutinia. This clade, a short-lived lineage known only from Asia, is here recognized as the family Rhombomylidae.
The skull of a new turtle from the Tiffanian (Paleocene) of the Goler Formation, Kern County, California is the first confirmed baenid from the Pacific slope of North America. Goleremys mckennai, gen. et sp. n., is represented by a nearly complete skull that shares two weak apomorphies with the latest Cretaceous and Paleocene genera, Stygiochelys and Palatobaena. The new genus appears to be the sister taxon of those eubaenine genera.
The best-known and most diverse mammalian faunas from the Fort Union Group of North Dakota are the Brisbane and Judson local faunas, both historically considered as mid Tiffanian (Ti3, mid-late Paleocene). Our review of the stratigraphic context of the localities provides no lithologic reasons for continued use of the terms Slope and Bullion Creek Formations, and we propose abandoning these terms in favor of the Tongue River Formation. Revised faunal lists were completed for this paper using taxonomic revisions published after the original 1978 study. The chronostratigraphic ranges of Brisbane and Judson taxa were then used to determine the biochronology of the faunas. The Brisbane local fauna is corroborated as being Ti3 based upon a combination of first appearance (Leptacodon tener, Thryptacodon australis, Dorraletes diminutivus) and last appearance (Pararyctes pattersoni, Ectocion collinus) data, together with taxa reported only from Ti3 faunas (Bisonalveus holtzmani, Plesiadapis rex, Aletodon quadravus). The Judson local fauna is reinterpreted as being late Tiffanian (Ti4) on the basis of the presence of Plesiadapis sp. cf. P. churchilli, or more importantly, the absence of P. rex. This reinterpretation of the age of the fauna means that Prochetodon foxi and Neoplagiaulax nanophus are restricted to the Ti4 biochron and Litocherus zygeus and Protictis paralus occur in the Ti3 and Ti4 biochrons.
Peratherium sp. cf. P. innominatum, a species with an early Wasatchian to Duchesnean range, is present in the Turtle Basin Local Fauna. Two new genera and species of rodents are described: Cristadjidaumo mckennai (Eomyidae) and Passaliscomys priscus (Heliscomyidae). The remainder of the rodent fauna consists of species that are similar to Duchesnean faunas from both the northern Great Plains (Saskatchewan) and from southern California. The probable occurrence of Simimys and Griphomys suggests a slightly greater similarity to the fauna of southern California.
Few researchers have attempted rigorous cladistic analyses of fossil ochotonids (pikas), largely due to the paucity and morphological conservativism of the fossils. However, pikas were diverse and widespread during the Cenozoic, and we therefore explore the applicability of cladistic analysis utilizing dental characters, which comprise most of their fossil record. We used abundant Barstovian ochotonid specimens from Hepburn's Mesa, Montana, and previously described Miocene material to construct a phylogeny and explore congruencies among the phylogenetic, stratigraphic, and geographic occurrence of Oreolagus from the western United States. Maximum parsimony analysis was conducted using 13 morphological characters. Stratigraphic and geographic occurrences of Oreolagus are generally congruent with the proposed hypothesis of phylogeny and seem to involve an early Hemingfordian first occurrence in the Great Plains, followed by later Hemingfordian and Barstovian radiations into and within the northern Rocky Mountain region, Oregon, and Nevada. Although this study is limited in scope, it illustrates that with further understanding of ontogenetic changes in occlusal morphologies of ochotonids, cladistic analysis is a viable method for reconstructing ochotonid phylogenies and exploring their biogeography.
Thick, steeply dipping, and generally conformable Upper Cretaceous and lower Paleogene strata are well exposed on the western Casper arch, central Wyoming. They record deposition prior to, during initiation of, and following onset of subsidence and basement-involved thrusting of the Laramide orogeny. Confusion has permeated the distributions, thicknesses, and ages of these strata, adjacent to the Wind River Basin's east-central margin. New lithostratigraphic mapping near Hell's Half Acre (HHA) revises identification of nonmarine units overlying the marine Lewis Shale (of Campanian and/or earliest Maastrichtian age). The homogeneous, mostly fine-grained Meeteetse Formation (MF) represents paludal conditions following deposition of the Lewis Shale's “lower tongue.” The local MF exceeds 3,200 feet (nearly 1.1 km) in thickness, almost 7.5 times greater than previously reported. The MF near HHA, although much thicker, exhibits characteristics strikingly similar to the Meeteetse elsewhere in the Wind River and Bighorn Basins. Most strata identified here as MF previously were considered as Lance Formation. The top of the MF near HHA matches the previously recognized contact with the Fort Union Formation (mostly Paleocene). Dominance of sandstone above that contact implies a more energetic fluvial regime that may, in part, represent latest Cretaceous time. Reflecting existing uncertainties, rocks above the MF and below the lacustrine Waltman Shale Member (Fort Union Formation) are designated here as “Fort Union (unnamed lower part) and Lance Formations, undifferentiated.” Upper surfaces of the Fort Union Formation were eroded early in Eocene time, and local scouring near HHA cut as deeply as the MF. Thus it is improbable that youngest parts of the Paleocene are recorded paleontologically in strata near HHA. The unexpectedly great thickness of the MF reflects onset of major, differential subsidence and provides evidence that the Laramide structural axis of the Wind River Basin originated several million years earlier than previously considered.
We provide a review of dental replacement features in stem clades of mammals and an hypothetical outline for the evolution of replacement frequency, mode, and sequence in early mammalian evolution. The origin of mammals is characterized by a shift from a primitive pattern of multiple, alternating replacements of all postcanines in most cynodonts to a derived pattern of single, sequential replacement of postcanines. The stem mammal Sinoconodon, however, retained some primitive replacement features of cynodonts. The clade of Morganucodon crown mammals is characterized by the typical mammalian diphyodont replacement in which antemolars are replaced by one generation in anteroposterior sequence, but molars are not replaced. The stem clades of crown mammals including multituberculates and eutriconodonts have an anteroposterior sequential and diphyodont replacement of premolars. By contrast, stem taxa of the trechnotherian clade (Zhangheotherium, Dryolestes, and Slaughteria) are characterized by an alternating (p2 → p4 → p3) and diphyodont replacement, a condition that is shared by basal eutherians. The sequential replacements of premolars in most extant placentals (either anteroposteriorly p2 → p3 → p4 as in ungulates and carnivores, or postero-anteriorly p4 → p3 → p2 as in some insectivores) would represent secondarily derived conditions within eutherians. The single replacement of P3/p3 of metatherians is the most derived for all therian mammals.
A new genus and species of dichobunid artiodactyl, Elaschitotherium qii, is described from the middle Eocene Shanghuang fissure-fillings of southern Jiangsu Province, China. This small form shares a number of dental features with North American homacodonts and the earliest hyperdichobunines (MP 13) from Europe, but it can be distinguished from both of these groups by several dental autapomorphies. E. qii shows greatest affinities with other Asian “dichobunoids” (Lantianius, and Eolantianius), and these three genera are tentatively united within a new subfamily of Asian dichobunids, the Lantianiinae. Lantianiines may be related to D. pakistanensis, but they do not seem to be closely related to other dichobunids from the early–middle Eocene of the Indo-Pakistani region. The occurrence of E. qii in Shanghuang suggests that bunoselenodont artiodactyls radiated synchronously in Asia, Europe, and North America. Further material is required to understand more fully the phylogenetic relationships among lantianiines and other subfamilies of European and North American dichobunids. However, it appears that the selenodont grade of dental adaptation was independently acquired in several lineages of dichobunids inhabiting the three northern landmasses during the middle Eocene. For the first time in Asia, early ruminants and dichobunids have been recovered in direct association at a single site—Shanghuang fissure D (Irdinmanhan ALMA). Further investigation of the Shanghuang artiodactyl fauna promises to improve our knowledge of the evolution of dichobunids in Asia. This, in turn, will shed new light on the origin of the Ruminantia and other extinct selenodont groups.
Vertical prism decussation, a microstructural reinforcement that toughens the cheek tooth enamel of the Rhinocerotoidea, is rare in mammals, where enamel is dominantly strengthened by horizontal decussation. Two hypotheses about the origin of this structure in rhinocerotoids are that it evolved through progressive tilting of the primitively horizontal decussation planes of early tapiroid-like ceratomorphs or that it appeared de novo in some taxon that had no decussation. However, no transitional taxa matching either of these criteria are known. New evidence from the earliest known rhinocerotoid, Hyrachyus, favors the second hypothesis, that vertical decussation arose from a primitive ceratomorph population that had lost most of the horizontal prism decussation characteristic of early ungulates. Hyrachyus has fully vertical prism decussation in its cheek teeth, confirming its relationship to rhinocerotoids, but the structure is poor in organization compared to that of later rhinocerotoids. Almost all mammals larger than insectivores generate sufficient dental stress to require microstructural reinforcement of their enamel, so the presence of poorly organized but fully vertical prism decussation and only faint traces of horizontal prism decussation in Hyrachyus indicate derivation from a taxon that had lost most of the horizontal decussation of primitive perissodactyls. In the late early Eocene ceratomorph Heptodon, whose trichotomous cladistic relationship to tapiroids and rhinocerotoids has been unresolved, there is evidence for considerable loss of enamel microstructural reinforcement, a condition that constrained these individuals to a diet of tender materials, possibly aquatic plant tissues, that required only low dental stresses during mastication. If derived from an enamel structure like that in Heptodon, the emergence of the new microstructurural organization in Hyrachyus would reflect a second dietary reversal producing higher occlusal stresses. The few other extinct lineages known to have acquired uniformly vertical prism decussation, the deperetellid tapiroids, astrapotheres and pyrotheres, may have undergone a similar sequence of dietary changes.
We describe and analyze the postcranial skeleton of Wasatchian rodents based on more than 30 new skeletal associations representing at least four genera and six species, all but one species attributed to Paramyidae. The limb skeleton of Wasatchian paramyids is relatively homogeneous across species and similar to that of extant sciurids. It shows a combination of arboreal and terrestrial features, often manifested in the same element, although in general the forelimb displays more arboreal features, whereas the hind limb is dominated by terrestrial traits. The skeletal anatomy of Wasatchian paramyids suggests that they were similar in locomotor behavior and habitat preference to the most generalized present-day squirrels, being more arboreal than Spermophilus and more terrestrial than Sciurus. They were probably equally adept on the ground and in the trees. In view of their antiquity and relatively basal position among Rodentia, Wasatchian paramyids provide important information on morphotypic conditions of the rodent postcranial skeleton.
The holotype and only known maxillary dentition of Deltatheroides cretacicus, collected in 1925 from the Upper Cretaceous Djadokhta Formation of Bayn Dzak, Mongolia, has teeth that are badly damaged and worn, obscuring many details of their structure. Reported is a new specimen of D. cretacicus collected in 2000 from the Red Rum (Kholbot) locality near Ukhaa Tolgod, Mongolia that preserves four molars. Although the teeth are worn and have suffered some damage, they preserve details missing from the holotype. Comparisons with other deltatheroidans reveal that D. cretacicus is most similar to Deltatheridium pretrituberculare, known from Bayn Dzak, Ukhaa Tolgod, and the younger Barun Goyot Formation.
In 1998, we published the first broadscale phylogenetic analysis of basal metatherians and relevant outgroups. That analysis is updated here with amendments taken from the new specimen of Deltatheroides cretacicus as well as from relevant literature appearing since our publication. As in 1998, the consensus trees in the updated analyses identify deltatheroidans as a basal clade of Metatheria, and Deltatheroides and Deltatheridium as more closely related to each other than to Sulestes from the Coniacian of Uzbekistan. Two isolated upper molars from the Albian–Aptian of Oklahoma and the Oldman Formation of Alberta, Atokatheridium boreni and cf. Deltatheroides sp., respectively, fall at a tetrachotomy with Deltatheroides and Deltatheridium, supporting a North American occurrence for a clade generally held to be Asiatic.
Very little is known about the extinct mammals and how many extant mammals are found in Eritrea. Data have been gathered with the objectives of clearly defining the extinct, extirpated and endangered mammals in Eritrea. Findings indicate that seventeen taxa of fossil and subfossil mammals in six orders were found in Eritrea, extending from the late Oligocene to the Holocene. Faunal correlation among paleontological sites in the Horn of Africa and East Africa indicate that the best close correlation are the Haïdalo site in Djibouti and the Chilga site in Ethiopia. Provisional findings on extant mammals indicate that for its small size, Eritrea is extremely diverse; it is predicted that similar species richness would be found for fossil fauna. Of the 132 species of mammals known from Eritrea, 114 are terrestrial. Of these, 71.1% of species are small mammals (less then 10 kg adult body mass), 73.7% are nocturnal, and about 21.9% are fossorial, a possible explanation why they survived hunting and the 30-year war between Ethiopia and Eritrea. It has been postulated that the center of evolution of some small mammal taxa might have been in Ethiopia; this hypothesis should be tested for Eritrea. The 11 extirpated and 8 endangered mammals in Eritrea are listed. From the 3rd century BC until the 20th century AD, elephants were sighted in areas where they are not found today. The observation of more than 28 elephants by Shoshani and colleagues in 2001 was a rare phenomenon for Eritrea; the previous last sighting of a large herd was 46 years ago. In 2003 at least 83 elephants were also observed. Elephants (Loxodonta africana) in Eritrea are endangered; being very large and a keystone species, protecting them would also preserve other animals and plants in the same ecosystem. The symbiotic relationship between elephants and doum palms is critical to the survival of these two species. Conservation programs must include public awareness and education, emphasizing the role animals play in a balanced nature. Protecting the unique natural heritage of Eritrea is an asset to be promoted through ecotourism for this and future generations. This report is the first combined account on the extinct and extant mammalian fauna of Eritrea. Prior to 1993 all publications concerning faunal assemblages from Eritrea were under the heading of Ethiopia, since Eritrea was a province of Ethiopia. Data presented here, it is hoped, will serve as a basis for future research on the paleozoogeography and neozoogeography of Eritrean mammals.
The Pawnee Buttes of northeastern Colorado lie within spectacular outcrops of Oligocene (White River Group) and Miocene (Ogallala Group) strata that form part of the Chalk Bluffs, an 150 mile long escarpment near the state line. These deposits were some of the earliest High Plains units to be explored by vertebrate paleontologists (Marsh, 1870; Cope, 1873). Consequently their fossil remains yielded the first information on North American faunas of mid- and late Tertiary time. Many parties subsequently exploited these deposits; their work, and his own investigations, were monographed by Galbreath in 1953. The present paper reviews the literature, a substantial part of the collections, as well as later stratigraphic work to present a revised litho- and biostratigraphy focused on the Pawnee Buttes area of eastern Weld County, Colorado. The oldest post-White River Group unit is the Martin Canyon Formation, the type locality of which is in adjacent Logan County. It contains an early Hemingfordian fauna as at its type section. The overlying Pawnee Creek Formation is restricted to the Weld County outcrops and is here differentiated from the younger Ogallala rocks formerly confused with it. The Pawnee Creek formation yields a latest early to early late Barstovian fauna that partially fills the hiatus between the classic Lower Snake Creek and Valentine faunas of Nebraska. Younger, but still early late Barstovian fauna, occur in the strongly disconformable undifferentiated Ogallala sands and gravels that underpin the High Plains surface. These assemblages have correlatives in the faunas of the lower part of the Valentine Formation of Nebraska.
New fossil mammal materials found in the upper Lingcha Formation of the Hengyang Basin, Hunan, China, include a complete skull of Hapalodectes hetangensis and a taxon new to the fauna, Dissacus zengi, n. sp. H. hetangensis is the morphologically least derived species of the genus and currently is the earliest known record of the genus. D. zengi, n. sp. is the second Asian early Eocene record of the genus and represents the last occurrence of the genus in Asia.
The Lingcha Formation includes two fossiliferous intervals. The upper contains about 12 species belonging to 7 mammalian orders, and the lower has yielded one mammalian species and one reptilian species. Biostratigraphic, chemostratigraphic, and magnetostratographic study in the Lingcha Formation indicates that the transient carbon isotope excursion that marks the Paleocene–Eocene boundary as currently advocated is present in the upper Lingcha Formation. The fauna from the upper Lingcha Formation occurs within the excursion interval, and is of earliest Eocene age. It is correlative with the Wasatchian-0 faunal zone in the Big Horn Basin, Wyoming, North America. The lower Lingcha Formation is of Paleocene age.
Six specimens of the rare taeniodont, †Stylinodon mirus, are recorded from the Lower part of the Adobe Town Member (TWkA1), Washakie Formation, Late Bridgerian–Early Uintan Land Mammal Age of the Washakie Basin. They are described and compared with other similarly aged specimens from other western North American basins. †S. mirus is the last of the taeniodonts, one of the early lines in the mammalian adaptive radiation that followed the demise of the dinosaurs. The most important of them is the articulated partial skeleton, FMNH PM 3895. It shows much new anatomical detail and it exhibits three notable specializations that provide a firm basis for speculation about its habitus. †Stylinodon inexplicatusSchoch and Lucas, 1981a, is shown to be a juvenile of †S. mirus, and is thereby put into synonymy with that species.
Cranial remains of Eumys elegans from Chalky Buttes, southwestern North Dakota, were examined and a composite diagram of a skull created. Eumys elegans is fully myomorphous and has a derived carotid artery circulation that is also found in some Old and New World muroids. Expansion of the posterior end of the jugal bone to form an articular surface that is part of the glenoid fossa is unusual in muroid rodents. The lower dentition is highly variable in both transverse crests and the connections of cusps to crests. Continuous variation in dimensions and heterogeneous molar crown morphology within individual tooth rows of a large sample of lower dentitions from Chalky Buttes suggest that only one, highly variable species was present. Variation in the upper dentition appears to be less. The rare enclosure of internal basins in the upper teeth parallels that development in other groups of muroids.
The fourth radiation of Camelidae in North America produced both living tribes of Camelidae: the Camelini of the Old World and the Lamini of South America. This paper focuses on the origin of Lamini. It places on record a new genus and species, Pleiolama mckennai, from the middle Miocene of Nebraska and Texas, and assigns to that genus the species P. vera (Matthew, 1909) from the late Miocene of the High Plains. Pleiolama is distinguished from four other extinct genera of Lamini recognized in North America. The nominal genus and species, Pliauchenia humphresianaCope(1875), traditionally thought to be an early representative of Lamini, is shown to be a nomen vanum.