Kenneth D. Rose

Early Eocene primates from Gujarat, India.

The oldest euprimates known from India come from the Early Eocene Cambay Formation at Vastan Mine in Gujarat. An Ypresian (early Cuisian) age of approximately 53Ma (based on foraminifera) indicates that these primates were roughly contemporary with, or perhaps predated, the India-Asia collision. Here we present new euprimate fossils from Vastan Mine, including teeth, jaws, and referred postcrania of the adapoids Marcgodinotius indicus and Asiadapis cambayensis. They are placed in the new subfamily Asiadapinae (family Notharctidae), which is most similar to primitive European Cercamoniinae such as Donrussellia and Protoadapis. Asiadapines were small primates in the size range of extant smaller bushbabies. Despite their generally very plesiomorphic morphology, asiadapines also share a few derived dental traits with sivaladapids, suggesting a possible relationship to these endemic Asian adapoids. In addition to the adapoids, a new species of the omomyid Vastanomys is described. Euprimate postcrania described include humeri, radii, femora, calcanei, and tali, most of which show typical notharctid features and are probably attributable to asiadapines. Anatomical features of the limb elements indicate that they represent active arboreal quadrupedal primates. At least one calcaneus is proximally shorter and distally longer than the others, resembling eosimiids in this regard, a relationship that, if confirmed, would also suggest an Asian or southeast Asian faunal connection. Isolated teeth from Vastan Mine recently attributed to a new eosimiid, Anthrasimias gujaratensis, appear to provide that confirmation. However, their attribution to Eosimiidae is equivocal. They are similar to teeth here tentatively referred to Marcgodinotius, hence A. gujaratensis may be a junior synonym of M. indicus. Corroboration of eosimiids at Vastan requires more compelling evidence. Although definitive conclusions are premature, available evidence suggests that the Vastan adapoids, at least, were derived from western European stock that reached India near the Paleocene-Eocene boundary.

High bat (Chiroptera) diversity in the Early Eocene of India

The geographic origin of bats is still unknown, and fossils of earliest bats are rare and poorly diversified, with, maybe, the exception of Europe. The earliest bats are recorded from the Early Eocene of North America, Europe, North Africa and Australia where they seem to appear suddenly and simultaneously. Until now, the oldest record in Asia was from the Middle Eocene. In this paper, we report the discovery of the oldest bat fauna of Asia dating from the Early Eocene of the Cambay Formation at Vastan Lignite Mine in Western India. The fossil taxa are described on the basis of well-preserved fragments of dentaries and lower teeth. The fauna is highly diversified and is represented by seven species belonging to seven genera and at least four families. Two genera and five species are new. Three species exhibit very primitive dental characters, whereas four others indicate more advanced states. Unexpectedly, this fauna presents strong affinities with the European faunas from the French Paris Basin and the German Messel locality. This could result from the limited fossil record of bats in Asia, but could also suggest new palaeobiogeographic scenarios involving the relative position of India during the Early Eocene.

Early Eocene lagomorph (Mammalia) from Western India and the early diversification of Lagomorpha

We report the oldest known record of Lagomorpha, based on distinctive, small ankle bones (calcaneus and talus) from Early Eocene deposits (Middle Ypresian equivalent, ca 53 Myr ago) of Gujarat, west-central India. The fossils predate the oldest previously known crown lagomorphs by several million years and extend the record of lagomorphs on the Indian subcontinent by 35 Myr. The bones show a mosaic of derived cursorial adaptations found in gracile Leporidae (rabbits and hares) and primitive traits characteristic of extant Ochotonidae (pikas) and more robust leporids. Together with gracile and robust calcanei from the Middle Eocene of Shanghuang, China, also reported here, the Indian fossils suggest that diversification within crown Lagomorpha and possibly divergence of the family Leporidae were already underway in the Early Eocene.

Postcranial Skeleton of the Early Eocene Mesonychid Pachyaena (Mammalia: Mesonychia)

ABSTRACT Analysis of postcranial skeletons of three species of the wolf- to bear-sized mesonychid Pachyaena from the early Eocene Willwood Formation, Bighorn Basin, Wyoming, indicates that it was a derived cursor combining specializations typical of modern Artiodactyla, Perissodactyla, and Carnivora. Skeletal anatomy supports the hypothesis, based on the dentition, that mesonychids evolved from Arctocyonidae. Numerous characters in the limb skeleton of Pachyaena are derived relative to Arctocyon, however, and resulted in restricted rotatory and mediolateral mobility at most joints, promoting predominantly sagittal movement. These characters, present in ungulates and cursorial carnivores, include a broad, caudally displaced humeral head; high greater tuberosity; proximal deltoid tuberosity; narrow, proximodistally elongate distal humeral articulation with moderately constricted capitulum; reduced epicondyles; deep olecranon fossa; anteriorly shifted radioulnar joint; posteriorly concave ulnar shaft; high g...

Skeleton of diacodexis, oldest known artiodactyl.

A nearly complete skeleton of early Eocene Diacodexis, the oldest known member of the mammalian order Artiodactyla, is described. Its slender, elongate limb elements indicate that Diacodexis was highly cursorial and closer in postcranial adaptations to tragulids and other primitive ruminants than to living or extinct nonruminant artiodactyls. Its skeletal specializations call into question the widespread notion that Diacodexis was the ancestor of all later artiodactyls.

New species of Batodonoides (Lipotyphla, Geolabididae) from the early eocene of Wyoming: Smallest known mammal?

A new early Eocene insectivore, Batodonoides vanhouteni , sp. nov., has molar teeth indicating a body size smaller than that of any mammal known to date. B. vanhouteni is the oldest known species assigned to the genus, which was known previously from the middle Eocene of California. The type, an associated maxilla and mandible, preserves P2–M2 and cl-p2, dp4, p4–m3, with alveoli for il–3. Some teeth (P4, c1, and p4) are still erupting, indicating that the specimen is a juvenile at about the age of dispersal. B. vanhouteni had two sets of functional teeth, unlike extant mammals of very small size. It retains the primitive pattern of cheek-tooth replacement, erupting P3 before P4, unlike the P4-before-P3 sequence of almost all Lipotyphla. The distribution of body masses for Clarkforkian and Wasatchian insectivores indicates that late Paleocene and early Eocene lipotyphlans occupied a lower range of body masses (ca. 1.3–53 g) compared to extant Lipotyphla (ca. 2.5– 1,100 g); the upper range of insectivore body masses was occupied by now-extinct “Proteutheria”.

STRATOCLADISTIC ANALYSIS OF PALEOCENE CARPOLESTIDAE (MAMMALIA, PLESIADAPIFORMES) WITH DESCRIPTION OF A NEW LATE TIFFANIAN GENUS

Abstract “Carpodaptes” jepseni is a morphologic intermediate between Carpodaptes and Carpolestes, with the number and position of cusps on p4 more consistent with placement in Carpodaptes but relative size of p4 more like Carpolestes. The type and only previously known specimen of “C.” jepseni, a partial dentary with p4–m2, is from Divide Quarry (Tiffanian Land-Mammal Age) in the Fort Union Formation of the Bighorn Basin, Wyoming. New specimens of “C.” jepseni from Divide Quarry include a nearly complete dentary with p4–m3 and alveoli for all anterior teeth, and the first known upper dentitions with P1–M2 and an alveolus for C1. Specimens of Carpodaptes cygneus are also described from Divide Quarry, demonstrating the occurrence of two distinct carpolestid species at the same locality. Stratocladistic analysis of the thirteen known carpolestid species, using thirty-two morphologic characters and stratigraphic order, produced eight most-parsimonious phylogenetic trees associated with a single cladogram. The topology of the cladogram generated using stratocladistics is identical to that of the single most-parsimonious cladogram from cladistic analysis of the same morphologic data, but stratocladistics allows greater resolution than cladistics at the level of phylogenetic trees. New specimens demonstrate extreme shortening of the anterior jaw of C. jepseni, a derived state not present in other carpolestids. This suggests that C. jepseni occupies a side-branch close to, but not at, the ancestry of the Carpolestes clade (an ancestor-descendant lineage composed of the sequence C. dubius, C. nigridens, and C. simpsoni, in that order). “C.” jepseni is here placed in a new genus, Carpomegodon.

Skeletal morphology and locomotor adaptation in Prolimnocyon atavus, an early Eocene hyaenodontid creodont

ABSTRACT Analysis of a recently discovered partial skeleton of Prolimnocyon atavus, an early Eocene creodont (Hyaenodontidae, Limnocyoninae), from the Willwood Formation of the Bighorn Basin, Wyoming, demonstrates that its postcranial skeletal anatomy was most similar to that of extant scansorial procyonid, viverrid, and mustelid Carnivora. Its anatomical traits (including reduced greater tuberosity, prominent and sharp deltopectoral crest, well-developed entepicondyle and brachial flange, ovoid radial head and gently concave, laterally oriented radial notch, moderately deep, laterally compressed ungual phalanges, medially projecting lesser trochanter, flattened talar trochlea with high lateral rim, helical proximal cuboid facet) are commonly associated with joint mobility and abducted limb posture which, in extant mammals, are characteristic of scansorial and ambulatory locomotion. These features resemble those of some early Eocene proviverrine hyaenodontids and, to a lesser extent, miacid Carnivora, but...

Extraordinary fossorial adaptations in the oligocene palaeanodonts Epoicotherium and Xenocranium (Mammalia)

New fossils of the rare Oligocene mammals Xenocranium and Epoicotherium add information on their skulls and provide the first information on their postcranial skeletons. These epoicotheres, the latest surviving palaeanodonts, have numerous fossorial adaptations and must have been predominantly subterranean. Their skeletal specializations are similar to, and equal or surpass in degree of development, those of most living fossorial mammals.

Postcranial skeleton of Eocene Leptictidae (Mammalia), and its implications for behavior and relationships

ABSTRACT The postcranial skeleton of early and middle Eocene leptictids is described based on several specimens from Wyoming and Colorado. Leptictids had a strongly keeled manubrium sterni, relatively short, generalized forelimbs (intermembral index ~60), a moderately robust humerus, stout metacarpals, and ungual phalanges resembling those of fossorial mammals. The femur is slender, with a narrow, elevated patellar trochlea and a posteriorly-directed lesser trochanter. The slightly longer tibia is firmly synostosed with the fibula just distal to midshaft. The fused tibiofibula forms a stable ankle joint with the deep astragalar trochlea. The astragalar neck and the metatarsals are moderately elongate, and there is a pronounced peroneal process on Mt I, probably related to pedal eversion. These traits indicate that leptictids were terrestrial mammals that progressed by quadrupedal walking, running, and hopping (possibly bipedally at high speed), and that burrowed using their forelimbs. Cladistic analysis o...