MAMMALIA 



343 



navigation. The skull was long and flat, and without horn?. The 

 canine teeth were tusk-like and were probably used for tearing out 



the succulent roots of water 

 plants. Everything seems to 

 indicate that it was a very 

 sluggish and stupid creature. 

 Dinoceras (Fig. 180) rep- 

 resents another family of am- 

 blypods and appears to have 

 been an end-product of a 

 long line of specializations. 

 It stood about seven feet 

 in height, had very heavy, 

 elephantine limbs and a mas- 

 sive body. The head was 

 armed with two heavy horns and great tusks, which were doubtless 

 used as a defense against the creodonts, the only contemporary ani- 

 mals that could have attacked a creature of such proportions. 



The archaic mammals nearly all became extinct before the end of 

 the Eocene. The causes of their extinction can only be conjectured. 



FIG. 179. A swamp-dwelling amblypod, 

 Coryphodon, Lower Eocene, North America. 

 (From Lull, after Osborn.) 



FIG. 180. Four-horned amblypod, Dinoceras, the culmination of its race, 

 Upper Eocene, Wyoming. (From Lull, after Osborn.) 



In some cases it seems probable that .over-specialization combined 

 with racial old age brought about extinction; in other cases it is more 

 likely that the competition against the on-coming modernized mam- 

 mals, which were more alert and intelligent, brought about their 



