中文摘要：

黄昏爪兽（Hesperotherium）是我国早更新世代表物种之一，因发现标本稀少，其形态特征和灭绝时间是存疑的。重庆市万州区盐井沟大垭口地点发现了多件Hesperotherium化石，其中多数骨骼属首次发现，新材料增加了我们对该类动物的骨骼形态学的认识，其后肢骨骼在进化过程中较为保守，可能正是这种进化过程中的保守性导致其不能适应第四纪多变的气候环境，最终灭绝。同时通过对已知含Hesperotherium动物群的分析，认为Hesperotherium可以作为早更新世早-中期的代表物种，对应于邱占祥命名的NCMQ 1或欧洲的维拉方中-晚期。

英文摘要：

Chalicothere is one of the most peculiar mammals in Pleistocene, characterized by bifid claws but not hooves as other ungulates. Hesperotherium is the most derived genus among Chalicotheriinae, and its morphology and extinction is still controversial. New specimens of this genus have been found from the Dayakou locality（30°37＇37.1＂N, 108°26＇56.9＂E） in Yanjinggou area, Wanzhou District, Chongqing Municipality, represented by four cheek teeth and ten phalanxes of pes, adding to our knowledge about chalicothere anatomy. The cheek teeth resemble Hesperotherium sinense from other localities in most respects. P2 and P3 lack the protoconule, and their paracone and metacone are not obviously separated on the ectoloph. The m2 is double V-shaped, and the ＂metastylid＂ will be fused with metaconid after worn. Some of the postcranial bones of this animal are discovered for the first time. The proximal facet of the pes proximal phalanx is large and inclines extremely in the dorsal direction. The pes medial phalanx is much depressed in the ulnar-radial section, with equally developed proximal volar and dorsal process. The pes distal phalanxes from Dayakou are broken, but they show the typical feature of chalicotheres known as the bifid claw. The morphology of pes phalanxes is similar with early chalicotheriines except the size somewhat larger or smaller, which indicating the evolution of the pes is conservative. Probably for this conservatism, chalicothere couldn＇t adapt to the climate fluctuation and became extinct in Early Pleistocene. By now, Hesperotherium fossils have been found from 17 Early Pleistocene localities in China and Myanmar（in figure 4）. The chronological analyses show that all these localities should be correlated to early to middle Early Pleistocene. In this view, we propose that Hesperotherium can be a representative genus of early to middle Early Pleistocene, equal to NCMQ（North China Mammal Quaternary）1 named by Zhanxiang Qiu or mid-late Villafranchian of Europe.