THE ORIGIN OF MAN 83 



oreodonts (an extinct group of niminating hogs 

 peculiar to America), giant pigs, armadillo-like 

 animals with leathery shields, and primitive dog- 

 like forms. Also there were many hoofed forms 

 such as the titanothers and the very characteristic 

 uintathers, mammals unlike anything living now, 

 and fleet-footed rhinoceroses. It was during the 

 Oligocene that mammals for the first time took 

 on a modern aspect, for here nearly all were pro- 

 gressive forms. In this period we get our first 

 knowledge of the varied mammalian life of the 

 plains and of grazing mammals. Rodents were 

 common, such as beavers, squirrels, pocket go- 

 phers, mice and hares. Among the ruminants, 

 peccaries were numerous, the entelodonts were of 

 large size, and the oreodonts, not unlike the pec- 

 caries and wild boars in appearance and size, were 

 exceedingly abundant, varied, and ran in great 

 herds. Among the carnivores, small dogs were 

 remarkably abundant and diversified. The last 

 of the archaic creodonts occurred here and as 



