甘肃东乡龙担的长鼻三趾马头骨化石--龙担哺乳动物群补充报道之三(英文)

A SKULL OF HIPPARION (PROBOSCIDIPPARION) SINENSE (PERISSODACTYLA,EQUIDAE) FROM LONGDAN,DONGXIANG OF NORTHWESTERN CHINA——Addition to the Early Pleistocene Longdan Mammalian Fauna (3)

报道了在甘肃省东乡县龙担地点发现的中国长鼻三趾马Hipparion(Proboscidipparion)sinense头骨化石。此前在早更新世龙担动物群中记述过的长鼻三趾马材料仅有一枚第三掌骨,头骨化石的发现不仅使该动物群的三趾马种级分类得到证实,同时扩大了对这个种头骨和牙齿特征的认识。由于最初建种的正型标本为老年个体,此后也未发现过中国长鼻三趾马的完好头骨化石,因此龙担的新材料将为该种的特征补充更多重要的信息,尤其是鼻切迹的构成。其鼻骨下部呈一细窄条状向前强烈延伸,组成鼻颌切迹下缘的后部,其前端尖,到达P2/P3界线水平,与前颌骨鼻突的末梢间有30mm的距离。这些特征的识别对判断长鼻三趾马的系统关系有重要意义。

A skull of Hipparion （Proboscidipparion） sinense is reported from the Longdan locality in Dongxiang,Gansu Province,northwestern China.The previously known material of H.（P.） sinense in the Early Pleistocene Longdan fauna was only a metacarpal III.The discovery of this skull not only confirms the specific identification of Hipparion in this fauna,but also increases the understanding of the cranial and dental characters of this species.The holotype specimen of H.sinense belongs to a senile individual,and no other complete skull of this species has been found.As a result,the new material from Longdan provides more key information for the diagnoses of H.sinense,and the structure of the nasal notch of this species becomes clear.The lower part of the nasal bone is a tenuous strip that extends far forward,comprises the posterior part of the lower margin of the nasal notch,and has a sharp anterior end reaching the level of the P2/P3 boundary,at a 30 mm distance from the posterior end of the nasal process of the premaxillary bone.The recognition of these characters is of great interest in determining the phylogenetic relationship of Proboscidipparion.