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We report 7 mammalian and 16 pollen species from the top of the Shimagou Formation in Kumkol Basin of northern Qinghai-Xizang Plateau,whose age is latest Middle Miocene (about 12.5 Ma).We erect a new species of fossil rodent,Spermophilinus kumkolensis sp.nov.The micromammalian fauna from the Kumkol Basin shares high similarities with contemporary faunas from Europe and northern China,indicating the existence of active zoogeographic exchange between Europe and northern Asia.Trees are dominant in pollen fossils,and herbs and shrubs are minorities.Broadleaved Quercus and Fagus predominate in tree pollens.The flora reconstructed by pollens displays a mixture of evergreen broadleaved forest and dry and warm steppe landscape.Compared to the modern vegetation in Yunnan region,the latest Middle Miocene flora in the Kumkol Basin represents a distinct vertical distribution.The ecotypes of the latest Middle Miocene fauna and flora in the Kumkol Basin,as a whole,are markedly different from those of modern animals and vegetation,the past climate being more suitable than today.