甘肃东乡几种早中新世哺乳动物化石

本文记述了在甘肃东乡椒子沟发现的几种早中新世哺乳动物化石:Gomphotherium sp、Dzungariotheriura orgosense、Rhinocerotidae gen. indet.和Paraentelodon macrognathus sp. nov.,着重讨论了全北区猪齿兽类的系统关系。根据化石的性质判断,东乡椒子沟化石点的地质时代应与欧洲Burdigalian早期,亦即MN_3相当或稍早。笔者将原定为上新世临夏组的第一、二岩性段划出,命名为椒子沟组,其时代为早中新世。

DISCOVERY OF SOME EARLY MIOCENE MAMMALIAN FOSSILS FROM DONGXIANG, GANSU

One of the authors of the present paper (Xie) was lucky enough to have purchased some interesting mammalian fossils from a drugstore, while visiting Dongxiang Autonomous County, Gansu Province, in 1986. Among the fossils there were teeth of giant rhinoceros, a fragment of proboscidean tusk and some odd-looking teeth later revealed to be of a very specialized entelodont. They were told to be found in a valley called Jiaozigou, some 10 km south-west of the town (fig. 1).Geologically speaking, the place where the purchased fossils were found is situated in the north part of the quite extensive Linxia Basin. According to the local geologists, who mapped the area during the seventies, the basin is filled with thick sequence of continental deposits called Linxia Formation. Based primarily on the finding of fossils of Hipparion fauna from the upper part of the sediments, the local geologists referred the whole Linxia Formation to Pliocene (former usage). The discovery of both giant rhinoceros and entelodont fossils in this basin naturally aroused the interest of the authors of the present paper, since the above mentioned animals lived mainly in Oligocene, at any rate, no later than Early Miocene.After several short visits to the place where the fossils in question were dug out, we succeeded in collecting more material of giant rhinoceros and entelodont by ourselves and in situ. Unfortunately, we failed to find any more of the proboscidean fossils. Although the color and the state of preservation of the fragment of the proboscidean tusk seems almost identical with those of some of the entelodont teeth and this seems to be in favor of the assumption that the proboscidean tusk came from the same site or from the same layer as the other specimens, we are still not fully certain whether this is really so.