A new cursorial hyena from Tibet, and analysis of biostratigraphy, paleozoogeography, and dental morphology ofChasmaporthetes(Mammalia, Carnivora)

Recent field work in the late Cenozoic Zanda Basin in southwestern Tibetan Plateau has provided new fossil evidence of vertebrate faunas spanning the late Miocene to Pleistocene, which represents new occurrences hitherto unknown in that region of Asia. In this paper we describe a new species of the cursorial hyaenid Chasmaporthetes, C. gangsriensis, sp. nov., from the Zanda Basin. Chasmaporthetes gangsriensis is smaller than other Plio-Pleistocene Eurasian records of the genus, and retains relatively wide premolars that are underdifferentiated in size. The m1 talonid has a trenchant hypoconid typical of Chasmaporthetes, but with a trigonid length-to-width ratio lower than all specimens referred to the genus. Metatarsal and phalangeal elements referred to C. gangsriensis are long and gracile, indicating cursorial abilities typical of Chasmaporthetes. With an age of early Pliocene (4.89–4.08 Ma), C. gangsriensis is morphologically the most basal Pliocene Chasmaporthetes in China, and is consistent with the ‘out of Tibet’ hypothesis for some Pleistocene megafauna. An analysis of nasal bone morphology revealed large intraspecific variation in extant spotted hyenas, showing that it is not a reliable criterion for species diagnosis in Chasmaporthetes. An evaluation of the biostratigraphic relationships among Asian and North American occurrences of Chasmaporthetes indicates that the genus first dispersed into the New World during the early Blancan North American land mammal age (NALMA) with likely ancestry close to the heterogeneous sample of C. lunensis in Eurasia. The possibility of a second dispersal is indicated by a mixed sample of specimens with significantly smaller p4/m1 length ratio than other Chasmaporthetes. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP