THE CRETACEOUS PERIOD 



271 



eaters. The Theropods lived through the whole Mesozoic, and 

 they have been found in many parts of the world. 



Ornithopods were in general appearance much like the Thero- 

 pods, but they were certainly plant-eaters, as shown by the tooth 

 structure (see Fig. 173). They were bipedal, the hind limbs 

 having only three functional toes, giving a sort of bird-like track. 

 The largest of these creatures measured 30 feet in length, and when 

 walking they must have stood 15 or 20 feet high. Ornithopods 

 ranged through all the Mesozoic except the Triassic. 



Fig. 172 

 A small two-legged Dinosaur, Podokesaurus holyokensis 

 (Talbot), from the Triassic of Massachusetts. Length, 

 less than 4 feet. Restored by Lull. (From a photo- 

 graph by Mrs. E. H. Terry of the model at Mount 

 Holyoke College.) 



Pterosaurs. — These were literal " flying-dragons" in Meso- 

 zoic time. They varied greatly in size from about that of a 

 sparrow to others with a spread of wing of 25 feet, which is about 

 twice that of any modern Bird. Not only did they include the 

 largest creatures which ever flew but, on account of their hollow 

 bones, their skeletons were wonderfully light. One finger of each 

 front limb was enormously lengthened to support the flying 

 membrane, as shown in Fig. 174. The other fingers were armed 

 with sharp claws. In general we may recognize two groups. 

 One group was typified by the Pterodactyl, which had a short, 

 stout body, short tail, and moderately long neck. The earlier 

 Mesozoic forms were supplied with sharp teeth, while the Creta- 

 ceous forms were mostly toothless. The other group, typified by the 

 Rhamphorhyncus (Fig. 174), had long tail, and in one species at least 



