Early Tertiary Tapiroidea of Asia. Bulletin of the AMNH ; v. 129, article 2

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New York : [American Museum of Natural History]
"Early Eocene tapiroids in Asia are known only from a single specimen, representing a form similar to the North American isectolophid Homogalax. The middle Eocene record is equally poor. One isolated lower molar of a form possibly ancestral to the late Eocene genus Teleophus is the only Asiatic tapiroid fossil of undoubted middle Eocene age. In beds that may be late middle or early late Eocene in age, Veragromovia, a genus based on a single upper molar, represents a form similar to the North American helaletid Helaletes, and Schlosseria, a better-known genus with a tridactyl manus, provides an approximate ancestor for the late Eocene genus Lophialetes. Several relatively rich late Eocene faunas reveal a great variety of tapiroids in Asia at that time. Whether this indicates an evolutionary radiation of tapiroids in the late Eocene or merely reflects uneven knowledge of the fossil record is a moot point. Early late Eocene (Irdin Manha age) tapiroids represent at least three families, the Helaletidae, known also in North America, and two newly recognized, solely Asiatic families, the Lophialetidae and the Deperetellidae. The helaletids include advanced species of Helaletes (formerly assigned to Desmatotherium) and a form similar to the North American genus Hyrachyus. The lophialetids are represented by the very abundant Lophialetes, a genus with rhinocerotoid-like molars, and a new genus, Breviodon, a small tapiroid with P[subscript]1-2 lost. A small form with P[superscript]1 lost and convex molar metacones may be related to Breviodon or may represent a distinct new genus. Two new genera, Rhodopagus and Pataecus, both diminutive forms, appear to be divergent offshoots from the Lophialetidae, in which the long molar ectolophs were lingually displaced and run parallel to or confluent with the metalophs. Early late Eocene deperetellids are represented by Teleolophus, a genus with bilophodont molars. In late late Eocene (Shara Murun age) Asiatic faunas, tapiroids are less abundant in both numbers and diversity. Helaletids are represented by species of Colodon, a genus also known in North America. Lophialetids, the dominant elements in early late Eocene faunas, are no longer present. Deperetellids are represented by Deperetella (including Cristidentinus and Diplolophodon), a descendant of Teleolophus in which the anterior premolars are disproportionately lengthened, in specialization for vertical shear. Indolophus, a poorly known Burmese genus, appears to represent an otherwise unknown tapiroid lineage and cannot be assigned to any existing family. Tapiroids are extremely rare in Oligocene deposits in Asia and are represented by only one genus, Colodon (including Paracolodon). Postcranial remains are known for Schlosseria, Lophialetes, and Deperetella. In all three genera the fifth metacarpal is reduced to a tiny vestige and the remaining metacarpals are relatively long and thin, indicating specialization for running. In Deperetella, elongate cervical vertebrae and a high radio-humeral ratio suggest a fleet, gazelle-like animal. It is suggested that the relatively great diversity of late Eocene tapiroids in Asia may be related to the scarcity of artiodactyls in the same faunas. The geographic distribution of late Eocene tapiroids in Asia provides no evidence for climatic zonation at that time. The occurrence of helaletid and isectolophid tapiroids in Asia supports other evidence for faunal exchange between Asia and North America during early and late Eocene time"--P. 261.
p. 183-263 : ill., map. ; 27 cm.
Includes bibliographical references (p. 262-263).