Abstract
The small mammals Myomiminae indet. (Gliridae), Leptodontomys cf. gansus Zheng and Li, 1982 (Eomyidae) and the new species Keramidomys sibiricus nov. spec. (Eomyidae) are described. They were collected from six layers of the middle to upper part of the Tagay-1 section on Olkhon Island. The glirid Myomiminae indet. is represented by only a few isolated teeth, the small eomyid Leptodontomys cf. gansus by a mandible with two teeth, and the second small eomyid Keramidomys sibiricus nov. spec. by several isolated teeth and a mandible. The ancestral tooth characteristics of Keramidomys sibiricus nov. spec. indicate an early evolutionary stage of Keramidomys in Asia. The suggested age of the assemblage is Early/Middle Miocene transition.