THE MUSCULAR ANATOMY AND THE RESTORATION OF THE TITANOTHERES 



707 



and later Tertiary ; and we still have surviving the very 

 diversely specialized end members of three families — 

 the tapirs, rhinoceroses, and horses. The divergent 

 trends of evolution in food habits and structure from the 



These divergent trends of evolution in the peris- 

 sodactyls are especially evident in the region of the 

 nostrils and lips. In the earliest true titanothere, 

 Eotitano'ps, the incisor and canine teeth and the whole 



Figure 644. — Relation of the contour of the head to the skull and jaws in living perissodaotyls 



A., Ehineroceros indicus (Indian rhinoceros); B, Opsiceros bicornis (black rhinoceros); C, Ceratoikerium simum (white rhinoceros); D, 

 JSquus (horse); E, Tapirus terrestris (tapir). In E the restriction of the nasals is associated with a marked outgrowth of the protrusile 

 proboscis. The angle of the mouth usually extends behind the anterior premolars, but in some species, as in the white rhinoceros, 

 it is in front of the tooth row. The nostrils are generally in line with the middle of the narial sinus. 



primitive Eocene perissodactyls to their latest descend- 

 ants are accordingly fairly well known, and we have 

 attempted to illustrate them in the series of restorations 

 of Eocene and later perissodactyls shown in Chapter IX. 

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front part of the jaws differed only in minor characters 

 from the same parts in the contemporary primitive 

 tapirs, rhinoceroses, and horses. Our restoration 

 of the head of Eotitanops resembles our previous 



