Abstract: Coryphodontids(Mammalia: Pantodonta), as the most geographically widespread major group of extinct large herbivorous mammals, are among the most useful mammalian index fossils for drawing stratigraphic correlations in North America(Lucas,1984,1998; Uhen and Gingerich,1995). In Asia, however, confusion regarding their taxonomy and misinterpretations of the lithostratigraphy of the fossil-bearing units have made it difficult to use coryphodontids for this purpose. Given improved understanding of intraspecific variation and sexual dimorphism within this highly variable taxon (Uhen and Gingerich,1995; McGee,2001,2002; McGee and Turnbull,2010), and the availability of newly clarified lithostratigraphic correlations(Meng,1990; Meng et al.,2007; Wang et al.,2010) and a recently established framework for Asian mammalian biochronology(Sun et al.,2009), it is an opportune time to restudy Asian coryphodontids. Specifically, Erlian Basin, Nei Mongol, China is one of the most important regions in the world for research in Paleogene vertebrate paleontology and stratigraphy, and has yielded some well-preserved coryphodontid material that can provide plenty of detailed information and clarify some taxonomic problems. Based on this material, Eudinoceras has been revised as follows.

摘要： 描述了在内蒙古二连盆地新采集的保存较完好的冠齿兽类化石。基于牙齿特征的比较认为：Eudinoceras kholobolchiensis Osborn & Granger, 1931、E. obailiensis Gabunia, 1961、Metacoryphodon luminis Chow & Qi, 1982和M.? minor Qi, 1987的个体大小、上前臼齿前尖V形脊角度、原尖前后棱发育程度、上下臼齿脊形化程度和尖脊形状及位置等特征与E. mongoliensisOsborn, 1924一致，应视为后者的次主观异名；M. xintaiensis Chow & Qi, 1982应归入Eudinoceras属，变更为E.xintaiensis; Metacoryphodon为无效命名，应予废除。厘定后的Eudinoceras属共含有6个有效种：E. zhichengensis Lei et al., 1987、E. youngi Xu, 1980、E. xintaiensis Chow & Qi, 1982、E.mongoliensisOsborn, 1924、E. crassum Tong & Tang, 1977和E. sishuiensis Wang, 1994。修订了Eudinoceras属和E. mongoliensis种的齿列特征。将二连盆地冠齿兽类化石的产出层位对应至该盆地重新厘定的地层框架中，E. mongoliensis集中在阿山头组，能确定的最早出现层位为阿山头组底部的AS-1层，最晚出现层位为阿山头组上部的AS-5层，其时代为早始新世中期，约为53~49 Ma。