甘肃省东乡族自治县龙担黄土底部新发现的哺乳动物群初步报道

龙担哺乳动物群发现于甘肃省东乡族自治县的早更新世黄土底部。此前我国早更新世的哺乳动物化石大多发现于河-湖相地层中,在黄土中极少发现,而且主要在六盘山以东。在龙担哺乳动物群中还发现了灵长类化石,这在我国西北地区尚属首次。龙担哺乳动物群产于黄土底部约30m的地层中,最低的层位距“底板”(积石组砾岩)仅约3m。化石相当丰富,其中有不少新的种类。目前已发现的化石共21种,大体可以分为3类:1)与泥河湾哺乳动物群相同或很接近的;2)与泥河湾哺乳动物群相比,在进化水平上稍低,因而可能代表较早地质时代的;3)在泥河湾哺乳动物群中没有发现过的。龙担哺乳动物群的地质时代可能比泥河湾者稍早,可能约2MaB.P.。其组成倾向于表明,当时该地区周围还有相当面积的森林覆盖。

NOTES ON THE MAMMAL FAUNA FROM THE BOTTOM OF LOESS DEPOSITS AT LONGDAN, DONGXIANG COUNTY, GANSU PROVINCE

The Longdan mammal fauna was discovered at the basal 30m of the Early Pleistocene loess deposits in Dongxiang County, Gansu Province. Prior to the present discovery, the Early Pleistocene mammal fossils were mostly found from fluvial lacustrine deposits, and predominantly confined to the east of the Liupanshan Mountain. The rich fossil assemblage contains many new forms. Twenty one species were identified and divided into three groups: 1) forms that are identical with or very similar to those of the Nihewan fauna, e.g ., Vulpes sp., Canis cf. C. chihliensis (pl. I 2), Pannonictis cf. P. pachygnathus , Pachycrocuta licenti (pl. I 4), Lynx sp., Nestoritherium sp., Coelodonta cf. C . nihowanensis (pl. II 1), and possibly Gazella sp.; 2) forms that appear more primitive than those of the Nihewan fauna, e.g., Meles sp., Megantereon cf. M. nihowanense (pl. I 3), Homotherium cf. H. nestianum , Sivapanthera sp. (pl.I 1), and Eguus sp. nov. (pl. II 2～3); and 3) forms that have not been found in the Nihewan fauna: e.g ., Sciuridae gen. et sp. nov., Macaca sp.,? Procynocephalus sp. (pl. I 5), Sinicuon sp., Felis cf. F. palaeosinensis , and Leptobos sp. (pl. II 4). In addition, the Longdan mammal assemblage is still missing some of the important elements in the Nihewan fauna, such as elasmothere, hyrax, camel, etc. The Longdan fauna is probably slightly older than the Nihewan fauna, here estimated as around 2Ma B.P. The primates, especially Macaca which mainly lives in woodland now, of the Longdan fauna indicate the presence of habitats suitable for the primates in Early Pleistocene in this area. In addition, the Longdan fauna also contains a low crowned chalicothere (Nestoritherium), a browser living in forest. The faunal composition suggests the presence of rather extensive forest coverage in the vicinity of the Longdan area. $$$$