CENOZOIC ERA: AGE OF MAMMALS 



613 



front teeth (incisors) in each jaw was longer than the others, giving 

 promise of the great tusks of the elephant and mastodon. Those 

 of the upper jaw were sharp-pointed and curved downward, while 

 those of the lower jaw were directed upward. The grinders (molars) 



LOWER PLIOCENE 

 UPPER MIOCENE 



MIDDLE MIOCENE 

 LOWER MIOCENE 



LOWER OLIGOCENE 

 UPPER EOCENE 



Tefrabelodon 



(shortening chin) 



Tetrabe/odon 

 (Sony c/?/s?J 



. Fb/epmastoc/o/7. 



asm — ^^* 



LOWER EOCENE , fc/totf c/r/i?) 

 (ancestor unknown/ ' 



Mastodon 



Tetrabe/odon 



Pa/eo mastodon 



Mo erifherium 



Fig. 548. — Chart showing the evolution of the elephant's head and teeth. 

 (Modified after Lull and Scott.) 



were somewhat ridged. The neck was of sufficient length to permit 

 the animal to reach the ground in feeding. 



The next elephant in the line of descent (Paleomastodon) (Fig. 

 548) appeared in the Upper Eocene and was larger and stockier, 

 with legs similar to those of its modern relatives. The upper and 



