甘肃临夏盆地的渐新世巨犀化石

描述了 2种巨犀化石 :霍尔果斯准噶尔巨犀 (Dzungariotheriumorgosense)和牙沟副巨犀(新种 ) (Paraceratheriumyagouensesp .nov.)。新种的主要特征是 :个体小 ;上颊齿齿冠高 ,有薄层白垩质覆盖 ;DP2～M1反前刺大 ,原尖后收缩沟明显 ,次尖有深的前收缩沟 ,中谷和后凹中常有附属小柱等。巨犀的演化历史可能比过去想象的更复杂。Indricotherium、Dzungariotherium和Paraceratherium为代表不同进化水平和支系的 3个属 ,不应合并为Paraceratherium一属。牙沟含巨犀化石层位的地质时代为晚渐新世。

INDRICOTHERES (PERISSODACTYLA,MAMMALIA) FROM OLIGOCENE IN LINXIA BASIN,GANSU,CHINA

The indricothere fossils from the Linxia Basin, Gansu Province, were first reported by Qiu et al. in 1990. The fossils were purchased from the Dongxiang county drugstore, allegedly from the deposits near the bottom of the Jiaozigou ravine. The age of the fauna was then considered as early Miocene because of the presence of a segment of proboscidean tusk among the purchased fossils. In 2002, while checking the fossils kept by a local dragon-bone dealer in the Hezheng County, the authors of the present paper found some well preserved Oligocene fossils, such as teeth of Tsaganomys, Aprotodon, some chalicothere, skull and teeth of indricotheres etc, allegedly from a ravine called Yagou of the Dongxiang County. Subsequent geologic work not only confirmed the provenance of the Yagou fossils, but also found that fossils from both Yagou and Jiaozigou ravines are from the same fossiliferous level, i. e., from the lower part of the Jiaozigou Formation. We failed to find any traces of proboscidean fossils in both localities. It is highly possible that the proboscidean tusk from the Jiaozigou ravine came from some overlying deposits, then mixed with the Oligocene fossils. Without the proboscidean fossils the lower part of the Jiaozigou Formation can well be assigned to late Oligocene, rather than early Miocene as previously suggested. The indricothere fossils are the best part of the Yagou fossils so far collected and may be of greater significance in age determination.