342 



VERTEBRATE ZOOLOGY 



cialized for rending of flesh than are those of the true carnivores. 

 Of the six families of creodonts recognized by palaeontologists, all 

 but one became extinct before the dawn of the era of modernized 

 mammals. Perhaps the best-known of the creodonts is the genus 

 Dromocyon, which is shown in the illustration (Fig. 177, C). It is 

 interesting to note that there were bear-like, dog-like, otter-like, cat- 

 like, and hyaena-like creodonts. 



The Condylarthra (knuckle-jointed) were archaic ungulates and 

 differed from the creodonta mainly in adaptations for herbivorous 

 diet. In form they closely resembled the creodonts, for both were 

 rather generalized in structure. The most interesting of the con- 

 dylarthrans is Phenacodus (Fig. 178), a form that for a long time 



was believed to be the five- 

 toed ancestor of the horse, 

 but is now known to be 

 both too specialized in some 

 respects and too late in its 

 appearance to have the 

 honor of playing this role. 

 Only a few species of con- 

 FIG. 178. Cursorial archaic mammal, con- dylarthrans are known and 

 dylarth, Phenacodus primcevus. Lower Eocene, ,, -, , 



North America. (Frm Lull, after Osborn.) these are S rou P ed mto 



two families. They range 



from the size of a fox to that of a large sheep. They had rather 

 tusk-like, but small, canines and low-crowned grinding teeth of 

 archaic pattern. The skull was long and low with a small brain 

 case. The feet were five-fingered and of a primitive plantigrade form, 

 with small hoofs. The genera that have been studied could not have 

 given rise to modern ungulates, but the real ancestors of the ungulates 

 must have been relatives of the condylarths. 



The Amblypoda (blunt-footed) were short-footed ungulate-like 

 mammals, some of which attained a huge size, almost comparable 

 with that of the elephants, but reminding one more of the rhinoceros 

 or hippopotamus types. There were four families of amblypods 

 that differed considerably among themselves. 



The genus Coryphodon (Fig. 179) is one of the best known ambly- 

 pods. It was probably a swamp-dweller, nearly as large as an ox, 

 but much more thick-set and massive. The limbs were short and 

 powerful, and the feet had spreading toes well adapted for swamp 



