Abstract
The Oligocene deposits of the Ulantatal area in Inner Mongolia (China) contain among the richest mammalian faunasfrom Asia. To date, only some parts of the rodent faunas have been described. Here, we propose to review the rodent faunal lists foreach site, including the description of a few new rodent specimens. We describe three additional rodent species: the CylindrodontidaeAnomoemys lohiculus, the Eomyidae Asianeomys sp., and the Dipodidae Litodonomys huangheensis. This study allows us toconstrain the stratigraphic range of Anomoemys lohiculus, which ranged from the late Early Oligocene to the early Late Oligocenein this area. Asianeomys sp. and Litodonomys huangheensis are dated from the latest Oligocene. These Oligocene deposits consistnow of more than 70 species of mammals if we include the fauna from Kekeamu. This latter corresponds to the basal part of theUlantatal Formation and could be dated biochronologically from the earliest Oligocene. When compared to the faunas from theValley of Lakes in Central Mongolia, the Ulantatal faunas present a great majority of rodents, and this difference can be partlyexplained by sampling and description biases regarding macro-mammals. This study also shows that variations existed betweenInner and Central Mongolia, especially regarding the composition of the rodent paleocommunities. However, the assessment of theirevolutionary history in this part of Asia with respect to the important climate and environment changes, require further precisionsand more material than current data allow.