EVOLUTION OP THE SKULL AND TEETH OF EOCENE TITANOTHBRES 



277 



therium zone, they had already shown considerable 

 specialization both in structure and in size. The 

 smaller and more primitive forms, such as E. gregoryi, 

 only slightly exceed Larabdotherium popoagicum in 



central digit — it still resembles Lambdotherium, as 

 shown in Figure 220. Its feet are adapted to softer 

 ground, and we may conjecture that it resembled the 

 tapir in its habits. 



Figure 230. — Reconstructed skeletons and restorations of Lambdotherium 'popoagicum (Ai, A2) and Eotitanops 



borealis (Bi, B2) 



Drawn by E. S. Christman under the direction of W. K. Gregory. About one-tenth natural size. These provisional reconstructions of skeleton 

 and body are based on material in the American Museum. 



size, but species like Eotitanops princeps and E. major 

 are little inferior to the existing American tapir 

 {Tapirus terrestris). The gradations in size between 

 these five or six species and mutations of Eotitanops 

 may be judged from the accompanying outlines (fig. 

 231) of the lower jaws. 



Eotitanops is a more typical titanothere than Lamb- 

 dotherium. In its limb structure it approaches espe- 

 cially Mesatirhinus, of the middle Eocene, although 

 in its mesaxonic foot structure — that is, its enlarged 



The principal contrasts 

 theres are the following: 



Lambdotheri um 

 Cursorial, light limbed, small, 

 like Eohippus. 



Face decidedly elongate. 

 Muzzle attenuate, pointed. 



Cranium abbreviate. 



Three premolars. 



Cropping teeth procumbent. 



between these two titano- 



Eotitanops 

 Cursorial to mediportal, small 



to large, almost equaling 



Tapirus. 

 Face moderately elongate. 

 Muzzle relatively abbreviate, 



broad. 

 Cranium intermediate. 

 Four premolars. 

 Cropping teeth more erect. 



