MES0Z0IC ERA: THE AGE OF REPTILES 



537 



beast, and morphe, form), because of the strong resemblance, both 

 in teeth and skeleton, to mammals. They are remarkable in pos- 

 sessing not only mammalian characters, but amphibian as well, 





. 



UPPjUF 



: 



- 



.; ■' -■<§ 



L 



I_ 



■ . m 



... ' ■'■-,!*. 



Fig. 499. — Skeleton of a mammal-like (theromorph) reptile, Endothiodon. 

 (Courtesy, American Museum of Natural History, City of New York.) 



and occupy a position intermediate between mammals and amphib- 

 ians. It seems probable that the Theromorpha include the pro- 

 genitors of the mammals. (Broom, 191 1.) One amphibian character 

 is seen in the backbone, the bodies of the vertebrae of which are 

 hollow at both ends (amphiccelous) and, in some cases, are only partly 

 connected with bone. The teeth 

 of certain genera (Cynognathus) 

 are of three kinds as in mammals : 

 incisors, canines, and molars. In 

 some cases the limbs are decidedly 

 mammal-like in structure. An- 

 other group of theromorphs have 

 toothless jaws (Figs. 499, 500), 

 covered with horn like a turtle's 

 (Oudenodon), and some possess, in 

 addition, two long canine teeth 



(Dicynodon). It is possible that the former (Oudenodon) is the 

 female of the latter. 



The theromorphs were all land animals, with limbs for the sup- 

 port of the body, but they varied greatly in appearance and habit. 



Fig. 500. — Skull of a theromorph 

 with beak-like jaw {Oudenodon). The 

 animal was herbivorous. The skull is 

 one and a half feet long. 



