内蒙古二连盆地沙拉木伦期啮齿类动物群研究

The Sharamurunian rodent fauna in the Erlian Basin,Nei Mongol,China

内蒙古二连盆地乌拉乌苏地区是亚洲哺乳动物分期中沙拉木伦期哺乳动物群的发现地和经典产地。在以往的研究中鲜少有关于这一地区啮齿类化石的报道。近来,在该地区沙拉木伦组下部地层中发现大量的啮齿类化石,经详细的形态学研究,它们被归入1超科4科7属9种,包括梳趾鼠超科的Yuomys cavioides,Gobiomys neimongolensis,G.exiguus以及G.asiaticus;跳鼠科Allosminthusuniconjugatus和Primisminthusshanghenus;仓鼠科Pappocricetodon rencunensis;壮鼠科Hulgana cf.H.ertnia和圆柱齿鼠科Proardynomys ulausuensis。乌拉乌苏沙拉木伦组下部与额尔登敖包“下红层”的啮齿类组合具有高度相似性,两者共同构成了二连盆地沙拉木伦期啮齿类动物群。综合二连盆地乌拉乌苏地点沙拉木伦组下部以及额尔登敖包剖面“下红层”的啮齿类化石,运用最小个体数的方法对二连盆地沙拉木伦期啮齿类动物群的组分和特征进行了分析,结果显示梳趾鼠类最具优势,跳鼠类和仓鼠类次之。通过物种多样性分析,二连盆地古近纪啮齿类动物群呈现出早中始新世以梳趾鼠类为主导类群到晚始新世以仓鼠、跳鼠类为主导类群的转变。内蒙古二连盆地和山西垣曲盆地沙拉木伦期啮齿类动物群的特征存在差异,很可能是由两个动物群所处不同的区域环境所造成的。

New middle Eocene rodent fossils discovered from the lower part of the Shara Murun Formation of Ula Usu,Erlian Basin,Nei Mongol,China,the classical locality of Sharamurunian mammalian fauna,were identified as 9 separate species(the ctenodactyloids Yuomys cavioides,Gobiomys neimongolensis,G.exiguus,and G.asiaticus,the dipodids Allosminthus uniconjugatus and Primisminthus shanghenus,the cricetid Pappocricetodon rencunensis,the ischyromyid Hulgana cf.H.ertnia,and the cylindrodontid Proardynomys ulausuensis)belonging to 7 genera,4 families,and 1 superfamily of Rodentia.The Ula Usu rodent assemblage shares a high degree of similarity with that from the“Lower Red”beds of the Erden Obo,and they both represent the typical Sharamurunian rodent assemblages found in northern China.The Sharamurunian rodent fauna in the Erlian Basin is analyzed by the minimum number of individuals based on the rodent materials from the lower part of the Shara Murun Formation in the Ula Usu and the“Lower Red”beds of the Erden Obo.In the Sharamurunian rodent fauna of the Erlian Basin,ctenodactyloids are the most dominant elements,and dipodids and cricetids follow next in prevalence.By analyzing the evolution of the rodent species richness in the Erlian Basin,the rodent faunas show a transformation from a ctenodactyloid dominant assemblage to a cricetid-dipodid dominant one in chronological order.The Sharamurunian rodent fauna from the Erlian Basin differs from that of the Yuanqu Basin and the differences in the rodent assemblages may be a response to the differences between the regional environments.