no 



THE AGE OF MAMMALS 



Of the archaic ungulates, the Hght-hmbed Condylarthra are now cer- 

 tainly represented by two genera of Phenacodontidaj {Tetraclccnodon, Eu- 

 protogonia), the former reported both from New Mexico and Montana. 

 Of the slow-moving Amblypoda the bunodont Periptychidse are still repre- 

 sented by four genera, and the selenodont Pantolambdidse, which are con- 

 sidered more nearly ancestral to the coryphodonts of the Wasatch, make 

 their first appearance. The genus Pantolambda, including animals rang- 



FiG. .30. — Basal and Lower Eocene stages in the evolution of the heavy-limbed Aniljly- 

 poda. Above : kSkeletons of the small Pantolambda and its large successor Coryphodon. 

 Below : Restorations of the same by Charles R. Knight. Both in the American Museum of 

 Natural History. 



ing in size from that of a large beaver to that of a sheep, receives its name 

 from the lambda shape of the cusps of its superior grinding teeth; out 

 of these simple cusps were destined to arise the extraordinary yoke- 

 shaped teeth of Coryphodon and the still stranger crested teeth of Uinta- 

 therium. The primitive skull, short limbs with everted elbows, the short, 

 spreading feet and long tail of this animal, all point toward ancestry from 

 an unguiculate or clawed animal of the primitive carnivore-creodont build. 



