Résumé
Oligocene ctenodactylid rodents of a rich mammalian fauna gathered by the Austrian expeditions to the Valley of Lakes (Central Mongolia) in 1996 and 1997 are described. The species recognized are already known from earlier fossil collections in the same area or from localities in Gansu (Shargaltein, Tabenbuluk) and Inner Mongolia (St. Jaques, Ulantatal) in China. A species only unformally described from Ulantatal (VIANEY-LIAUD, SCHMIDT-KITTLER & MARIVAUX 2006) is erected as new taxon Huangomys frequens nov. gen. nov. sp. Thanks to the stratigraphically controlled gathering of fossils in the sections more precise biostratiographical correlations can be established with the well studied faunal succession of Ulantatal. Comparison based on Karakoromys, Huangomys nov. gen. and Yindirtemys reveal that the levels A and B of the Valley of Lakes correspond to the lower part of the Ulantatal sequence. Most of the middle part of the Ulantatal section has no representation in the Valley of Lakes series because of a sedimentary gap. Level C and C1 can be correlated with the upper part of the Ulantatal section. As to the phylogenetic results, Tataromys, Alashania VIANEY-LIAUD et al. and Huangomys nov. gen. are most probably members of one and the same branch of specialization from which Yindirtemys probably diverged more early. Karakoromys seems to be very close to the bifurcation point of the two developmental directions. It shows the most ancestral status of all Tataromyinae