The eomyid rodents (Mammalia) from the Oligocene and Miocene of the Valley of Lakes (Central Mongolia)

Abstract

We report new discoveries of eomyid rodents from the Valley of Lakes (Central Mongolia) yielded by diverse layers ranging in age from the Early Oligocene (local biozone A) to the Late Miocene (local biozone E). The remains of eomyid rodents are relatively rare compared to other groups of fossil rodents found in the same region. All together, eight taxa have been identified: Eomys cf. orientalis (biozone A), Eomys aff. orientalis and Eomys sp. (biozone B), cf. Asianeomys bolligeri (biozone C), Asianeomys dangheensis (biozones C1 and D), Eomyops/Leptodontomys sp. and Keramidomys sp. (biozone D1/2), and Omboomys builstynensis gen. nov., sp. nov. (biozone E). A progressive change of dental morphology and size indicates that the genus Asianeomys represents a local evolution of the genus Eomys in Asia, but also suggests the possible existence of a lineage including Eomys cf. orientalis, Eomys aff. orientalis, cf. Asianeomys bolligeri, and Asianeomys dangheensis.