Abstract: The dipodid fossils from the red mudstone of the Lower Member of the Xianshuihe Formation include eight species of four genera: Parasminthus asiae—centralis, P. tangingoli, P. parvulus, Parasminthus sp. I, Parasminthus sp. II, Ltodontomys huangheensis gen. et sp. nov., Heterosminthus lanzhouensis sp. nov., and Sinosminthus sp. The new genus Litodontomys can be diagnosed as: having proportionally wider and shorter cheek teeth, with simpler occlusal pattern, well developed lophids, mesolophid short or absent, ectolophid extending from protoconid. The new species Heterosminthus lanzhouensis represents a primitive species of Heterosminthus. The main cusps of its molars are slightly alternate in position. The protoconule is distinct but the anterostyle is absent on Ml/ 2. ml has developed mesolophid, bending ectolophid, and antero-buccally oblique ectomesolophid. The dipodids described above are similar to those of Taben buluk in composition. The middle part of the lower red mudstone beaHng the dipodids may be equivalent to that of the latter in age. It is of late Oligocene. The phylogenetic relationships or the Paleogene dipodids are analyzed based on dental features using PAUP 3.1. l. The predominance of the dipodids in the late Oligocene micromammals in the Lanzhou Basin indicates that a grassland or savanna habitat might have been established in the Lanzhou area during that time.