Tlie Rise of the MammaU 



and the one with which we ai'e best acquainted, 

 is P. primcBvus, 



The body and tail of this animal were long, 

 the back arched, the legs stout and of moderate 

 length, and there were five toes on each foot — 

 all points in which Phenacodus resembled the 

 early carnivores. The outermost toes did not 

 reach the ground, but while the animal was not 

 quite plantigrade, it did not walk on the tips of 

 its toes, as do modern ungulates like the sheep 

 and deer. The animal was evidently omnivo- 

 rous, and as it possessed neither claws nor sharj) 

 teeth, it must have sought safety in flight. 

 Phenacodus is a typical member of the group 

 of primitive hoofed quadrupeds from which all 

 modern ungulates are believed to be descended. 

 It is of additional interest from the relation- 

 ships it shows to other groups, and notably to 

 the clawed animals, from which those mth 

 hoofs are thought to have branched off at an 

 early date. This interest is enhanced by the 

 fact that its discovery fulfilled a generalization, 

 one might say prophecy, of Professor Cope, to 

 the effect that the primitive types of hoofed 

 223 



