EOCENE AND OLIGOCENE TITANOTHERES OF MONGOLIA 



933 



cranium is unknown, no direct comparison can be 

 made with either Dolichorhinus or Protitanotherium; 

 yet from the extreme depth of the jaw in comparison 

 with American species we may be confident that the 

 skull was relatively high and deep as well as long. 



lower borders. The incisors are the largest known 

 among the titanotheres, especially the second pair. 

 The canines are very large and pointed — sublanceo- 

 late. The premolars have prominent crowns and 

 highly sculptured internal cingula. The posterior 



,■ cranium (Am. Mus. 



Figure 788. — Referred cranium and jaw of Protitanotherium 



20254), paratype jaw (Am. Mus. 20251) 



One-sixth natural size. This composition of male cranium and jaw exhibits the elongate frontonasal horns and the long 

 shovel-shaped nasals characteristic of Protitanotkerium. To correct the crushing of the parieto-occipital crest in the 

 original specimen the occiput has been raised after the manner of Protitanotherium. The crushed premaxilla is also restored. 

 The jaw (Am. Mus. 20251) is reversed from the left jaw of the opposite side. The superior view of this cranium shows 

 the extensive restoration and the placing of the crushed fragments in their approximate position; it also illustrates the 

 saddle-shaped broadening of the top of the cranium between the lambdoidal crests, and the rounded, elongate frontal 

 horns resting upon the nasals. 



In the American species the bony horns are very 

 rudimentary and the canine tusks are sharp and 

 powerful. The jaws contrast widely with those of 

 Dolichorhinus and of Protitanotherium not only in 

 their prodigious size but in the great depth of the 

 mandibular rami, of the chin processes, and of the 



molars are exceptionally long and relatively narrow, 

 the breadth-length index being 82 as compared with 

 98 in Dolichorhinus and 1 15 in Brontops Irachycephalus. 

 Certainly the habits and probably also the habitat 

 of Telmaiherium differed widely from those of either 

 Dolichorhinus or Protitanotherium. 



