The first discovery of late Cenozoic small mammalian faunas in the south of eastern Transbaikalia

Pliocene and Pleistocene deposits in the south of Eastern Transbaikalia form a bleached sand mass. They have been comprehensively studied in recent decades. Five formations have been recognized there and characterized by pollen and mollusk fauna. Absolute datings have been obtained for some of these formations. However, no fossil remains of small mammals have been described in this region. Our recent studies pioneered the collection of Late Pliocene and Pleistocene remains of lagomorphs and rodents from five localities. Investigation of these fossils has revealed at least three faunas similar to Western-Transbaikalian ones: Chikoi, Tologoi, and Upper Paleolithic faunal assemblages. The most ancient fauna found in Eastern Transbaikalia is represented by the Late Pliocene Chikoi faunal assemblages with Villanyia and Prosiphneus. The next Early Pleistocene fauna includes representatives of the Tologoi faunal assemblage: Eolagurus simplicidens, Myospalax wongi, and Lasiopodomys brandti. Upper Pleistocene fauna of Eastern Transbaikalia consists of species of Upper Paleolithic faunal assemblage. The presence of the listed species, widespread in Northern China, Mongolia, and Western Transbaikalia, allows correlation of Late Pliocene and Pleistocene faunas and deposits of these regions.