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.