902 



EOCENE AND OLIGOCENE TITANOTHERES OF MONGOLIA 



Figure 763. — Map of eastern and central Asia 

 showing (3, 4) tlie area of central Mongolia 

 explored by the American Museum Asiatic 

 expedition of 1922 and 1923. After Osborn, 

 May 25, 1923, p. 2, fig. 1 



Witbin the four circles shown are the middle Oligocene ex- 

 posures of southern and central Asia in which remains of 

 the giant hornless rhinoceros Baludiittinium have been 

 discovered: 1, Bugti beds of Baluchistan, yielding the type 

 of Baluchitherium osborni: 2, Indricotlierium ( = Baluchi- 

 therium) zone of Tmgai, northern Turkestan; 3, Baluchi- 

 tferiuvi gra-ngcri zone (Houldjin formation), southeastern 

 Mongolia; 4, Baluchitherium gravgeri type zone (Hsanda 

 Gol formation), central iSIongolia. Upper Eocene and 

 lower Oligocene titanotheres occur near area 3. Certain 

 upper Eocene species of titanotheres and of amynodonts 

 are also found in Burma along Irrawaddy River. 



Figure 764. — Route map of the American Museum expedition of 1922 and 1923 in southeastern and central Mongolia, show- 

 ing the three localities where titanotheres were discovered. After Berkey and Granger, May 25, 1923, p. 2, fig. 1 



The three localities are the Iren Dabasu Basin, in which lies the Irdin Manha formation (Protitanotherium grangeri zone) , upper Eocene, on the Kalgan-Urga 

 trail; Shara Murun (Ptotitanothenum mongoliense zone), uppermost Eocene, on the Kalgan-Sair TJsu-TJliassutai trail; and Ardyn Obo (Brontops gobiensis zone), 

 lower Oligocene, on the Kalgan-Sair Usu-XJliassutai trail. These and other fossil fields are indicated by local Mongol names employed to designate the 

 respective formations. 



