912 



EOCENE AND OLIGOCENE TITANOTHERES OF MONGOLIA 



guyotii of horizon C? or D of the Bridger formation 

 of Wyoming (middle Eocene). Osborn (November 

 10, 1924) described as Eudinoceras mongoliensis a 

 large upper Eocene amblypod related to the Dinoceras 

 of Marsh and to the Loxolophodon of Cope, animals 

 sm^viving to the upper Eocene horizon B of the 

 Uinta Basin of Utah. Osborn also described (Novem- 

 ber 11, 1924) Andrewsarchus mongoliensis, a giant 

 creodont of the family Mesonychidae, which attained 

 its zenith in the upper Eocene (Uinta B horizon) of 

 North America. 



Protitanotherium grangeri lij^e zone. — On studying the 

 fauna of the Irdin Manha formation, Osborn (1925) 



Telmatherium berkeyi, represented by seven specimens, jaws 

 and teeth. 



Dolichorhinus olseni, represented by one specimen, a pair of 

 jaws. 



Manteoceras? irdinensis, represented by one jaw; generic 

 reference doubtful. 



Metarhinus? mongoliensis, represented by one jaw and two 

 teeth; generic reference doubtful. 



By far the most abundant mammal of the Irdin 

 Manha formation is the small lophiodont {Desmato- 

 iherium mongoliense) , represented by innumerable 

 specimens. Next in abundance are the titanotheres. 

 The carnivorous Creodonta, especially the family Meso- 

 nychidae, are very common. Of the family Mesonychi- 



FiGURE 772. — Irdin Manha formation (upper Eocene of Mongolia, Protitanotherium grangeri zone) 

 Irdin Manha bluff, looking northward across the Ealgan-Urga trail. After Am. Mus. negative No. 251584, by R. C. Andrews 



assigned to the formation the name Protitanotherium 

 grangeri life zone because of its content of the charac- 

 teristic mammalian titanothere Protitanotherium gran- 

 geri. It contains also, however, remains of Telma- 

 therium ierlceyi and Dolichorhinus olseni, as well as 

 of other species. The species Protitanotherium gran- 

 geri and Dolichorhinus olseni are much more primitive 

 than their successors Protitanotherium mongoliense 

 and Dolichorhinus Icaiseni in the Shara Murun forma- 

 tion; consequently the Irdui Manha formation is 

 older than the Shara Murim formation. The Irdin 

 Manha formation has yielded remains of 23 or more 

 titanotheres and chalicotheres. The following hst 

 ■shows the relative abundance of five species : 



Protitanotherium grangeri, represented by thirteen skulls 

 and jaws and other skeletal remains. 



dae the skull of Andrewsarchus mongoliensis is of great 

 size and is well preserved. The rhinoceroses are 

 represented by the Hyracodontidae {Caenolophus, 

 Lophialetes) and probably by the Amynodontidae 

 (Amynodon), both types rare in this formation. All 

 other mammals (artiodactyls, rodents) are rare. The 

 giant amblypod Eudinoceras mongoliensis is repre- 

 sented only by two teeth. 



MIDDLE (?) EOCENE: AESHANTO FORMATION 

 Berkey and Morris (October 7, 1924, p. 119) 



Locality and lithology. — Twenty mUes southeast of 

 Iren Dabasu, in the Irdin Manha Basin, at the base of 

 the Irdin Manha section, is a lower series of red beds to 

 which the name Arshanto is given. 



Beneath the titanothere beds [Irdin Manha] there are red 

 clays, provisionally called Arshanto, probably to be correlated 



