Abstract: Some material of Protitan is discovered by the staffs of IVPP and Dinosaur Museum of Erlianhot city from Late Eocene Tukhum beds in Erden Obo (Urtpn Obo) area of Siziwangqi, Nei Mongol during the summer field season of 1991. This is the first discovery of giant mammal from Tukhum beds in Shara Murun area. The material includes a third lower molar and several isolated bones. All of them are found in one square meter, and we believe that they represent an individual (V10104—1 VPP number). At present, a total of 4 species are found in Tukhum beds: I. Teilhardia pretiosa; 2. Lophialetes expeditus?; 3. Protitan sp. (V10104); 4. a small carnivore (unpublished).