914 



EOCENE AND OLIGOCENE TITANOTHERES OF MONGOLIA 



identified. The 10 species of these 7 genera are geo- 

 logically distributed in ascending order in the Irdin 

 Manha (upper Eocene), Shara Murun (summit of 

 Eocene), and Ardyn Obo (lower Oligocene) forma- 

 tions, as shown in the accompanying table (p. 907). 

 The discovery in Mongolia of 10 species belonging to 

 these 7 genera of titanotheres confirms the generic con- 

 ceptions and definitions of the American paleontolo- 

 gists Marsh, Hatcher, Wortman, and Osborn. 



The seven generic names assigned to these species 

 accord with those already established for the American 

 specimens, namely: 



Figure 773. — Type lower jaw of Protitanotherium grangeri (Am. Mus. 20103) from the 

 upper Eocene Irdin Manha formation of Mongolia 



Probably a female specimen. Found at the locality indicated by a + in Figure 771. A, Side view; B, superior 

 view. One-sixth natural size. 



Metarhinusf, the diminutive amphibious Utah and Wyoming 



titanothere of Osborn. 

 Manteocerasf, the "prophet-horned" titanothere of Hatcher- 



Wortman. 

 Prolitanotherium, the ancestor of the Tilanotherium of Hatcher. 

 Telmatherium, the "swamp" titanothere of Marsh. 

 Dolichorhinus, the "long-nosed" titanothere of Hatcher. 

 Brontops, the "thunder-eyed" titanothere of Marsh. 

 Menodus, the "long-headed" titanothere of Pomel. 



Most of the names assigned to species of these gen- 

 era either refer to the region in which these remarkable 

 specimens were found or are given in honor of the men 

 who were instrumental in discovering them, namely: 



Protitanotherium mongoliense, the titanothere first named fron^ 



Mongolia. 

 Brontops gohiensis, the lower Oligocene "thunder-eyed" titano- 

 there of the Gobi Desert. 

 Menodus mongoliensis, the first Menodus found in Mongolia. 

 Protitanotherium andrewsi, named in honor of Roy Chapman 



Andrews, leader of the third Asiatic expedition. 

 Protitanotherium grangeri, the first titanothere found in Mon- 

 golia, named in honor of Walter Granger, chief paleontologist 

 of the expedition. 

 Telmatherium berkeyi, named in honor of Charles P. Berkey, 

 chief geologist of the expedition, who picked up the first 

 titanothere jaw. 



Dolichorhinus kaiseni, named in honor of 

 Peter Kaisen, who explored the Kaisen 

 quarries of Ula Usu, Shara Murun for- 

 mation. 

 Dolichorhinus olseni, named in honor of 

 George Olsen, who discovered many 

 fine titanotheres and was chief prepara- 

 tor of the titanothere collection. 

 Manteocerasf irdinensis, named in refer- 

 ence to its discovery in the Irdin Manha 

 formation. 

 Metarhinusf mongoliensis, named in refer- 

 ence to its discovery in Mongolia. 



The Ardyn Obo formation ap- 

 pears to represent the lower 

 Oligocene, because the species 

 Brontops gohiensis is very similar to 

 certain species of Brontopinae, such 

 as Brontops Irachycephalus and 

 Teleodus avus, found in the base 

 of the Chadron formation, Titano- 

 therium zone. South Dakota. 



In the probably younger Oligocene 

 formations of Mongolia known as 

 the Houldjin and Hsanda Gol no 

 remains of titanotheres have been 

 discovered; the giant hornless rhi- 

 noceroses known as BalucMtherium 

 grangeri are there the predominant 

 mammals. 



It therefore appears probable that 

 the Brontotheriidae became extinct 

 in Mongolia in the beginning of lower Oligocene time, 

 whereas in western North America that family flour- 

 ished and attained its zenith at the end of lower 

 Oligocene time, when it suddenly became extinct. 



These discoveries are historically so interesting that 

 it appears desirable to give a complete list of the 

 specimens of Mongolian titanotheres, some of which 

 will in time be exhibited in, the United States National 

 Museum and other great museums of this and other 

 countries. In this list the numbers are those assigned 

 to the specimens in the American Museum of Natural 

 History. 



