EOCENE AND OLIGOCENE TITANOTHERES OP MONGOLIA 



925 



the grinders and the offensive power of the canines, 

 which are relatively large, especially in the robust 

 males. The incisors are of medium size with obtuse 

 cingula, diminishing in size from the lateral to the 

 median, the summits tending to become rounded and 

 obtuse in P. andrewsi. As in the American species, 

 the superior and inferior premolars become progres- 

 sively molariform. 



Comparative measurements of three species of Protitanotherium, 

 in millimeters 



Protitanotherium granger! Osborn, 1925 



Original reference. — Osborn, H. F., Upper Eocene 

 and lower Oligocene titanotheres of Mongolia: Am. 

 Mus. Novitates No. 202, 1925. 



Type locality and geologic level. — Half a mile south 

 of the Kalgan-Urga telegraph line, southeastern Gobi, 

 Mongolia; Irdin Manha formation (upper Eocene, 

 Protitanotherium grangeri zone). 



Materials. — Our knowledge of this species is based 

 on the materials found north and south of the Kalgan- 

 Urga telegraph line, including the type (Am. Mus. 

 20103), female skull and jaws well preserved, incisors, 

 canines, fragmentary molars, also four specimens (Am. 

 Mus. 20120, 20122, 20123, 20126) found 2 miles north 

 of the telegraph line, one specimen (Am. Mus. 20105) 

 found 1 mile north of the telegraph line, another (Am. 

 Mus. 20108) found half a mile north of the telegraph 

 line, four (Am. Mus. 19179, 20113, 20114, 20119) 

 found half a mile south of the telegraph line, two 

 (Am. Mus. 20112, 20110) found 1 mile south of the 

 telegraph line, and one (Am. Mus. 20104) found half 

 a mile west of the telegraph line. 



This very rich and abundant material is supple- 

 mented by remains of fore and hind limbs of both the 

 right and left sides (Am. Mus. 20171) belonging to 

 several individuals. Consequently, while we know 

 the cranial and dental characters of Protitanotherium 



grangeri of both sexes perfectly, we have still much 

 to learn regarding the skeleton. 



Specific characters. — The exceptional features of the 

 type cranium (Am. Mus. 20103), such as (a) the 

 horseshoe-shaped concavity bordering the posterior 



Figure 781. — Protitanotherium grangeri, Am. Mus. 20103 (type) 

 A well-preserved female skull and jaws, with incisors, canines, and fragmentary 

 molars, altered by vertical crushing of the symphyseal region of the jaw. Dis- 

 covered half a mile south of the Kalgan-Urga telegraph line. A, Lateral view, 

 right side; Ai, lower jiw, superior view; A^, skull, inferior view; A', skull, 

 superior view. Original drawing. One-tenth natural size. 



nares and (6) the deep pits on either side of the pre- 

 sphenoid, characters observed also in specimens of 

 Dolichorhinus (a) and of Sphenocoelus (&), led us at 

 first to regard this type as related to the above genera. 

 The real propinquity of the species grangeri to Pro- 

 titanotherium is, however, firmly established by the 



