MESOZOIC ERA: THE AGE OF REPTILES 



5S9 



those in the back of the jaw were small and sharp, with a sawlike 

 edge. This pterosaur could probably walk on all fours or on its hind 

 legs alone. When standing on its hind legs, it was less than two feet 



Fig. 519. — A Jurassic pterosaur {Dimorphodon) . The extreme length from the tip 

 of the nose to the end of the tail was a little more than three feet. (Modified after 

 Seeley.) 



high, and its wings had a spread of a little more than four feet. The 

 wings (Fig. 519) were formed by a naked membrane, without feathers 

 or hair, stretching from the body to the greatly elongated fourth fin- 

 ger. Although the least specialized of the pterosaurs, they possessed 

 few characters connecting them with other reptiles. 



Perhaps the most highly specialized animal that ever existed was 

 a pterosaur (Pteranodon ; Greek, pteron, wing, and a-odont-, without 

 a tooth) that lived 

 in the Upper Creta- 

 ceous. In this animal 

 (Fig. 520) it would 

 seem that every- 

 thing possible was 

 sacrificed for flight. 

 The upper portion of 

 the body, the wing, 

 shoulder, and breast 



Fig. 520. — Skeleton of Pteranodon, the most highly 

 specialized of the pterosaurs (Cretaceous). Everything 

 was sacrificed for flight and feeding. The wings measured 

 almost twenty feet from tip to tip. (After Eaton.) 



were all extraordi- 

 narily strong, while 

 the lower portion of 

 tKe body and hind 

 limbs were very weak. The head was highly developed, being long 

 and slender, with a dagger-like beak and toothless jaws. The head 

 was about four feet long, the body only slightly longer. It is thought 



CLELAND GEOL.— : .^6 



