Chap. 35 REPTILES FIRST LAND VERTEBRATES 727 



while the promise of mammalian life was still hidden in small meat-thirsty 

 carnivores that ate the large yolk-filled eggs of the reptiles (Fig. 35.2). 



Among the earliest reptiles were three types from which a varied host of 

 animals originated. One side -line of those (Cotylosauria) with sprawling legs, 

 heavy bodies and remarkable armor were the ancestors of turtles. In another 

 side line were the mammal-Uke reptiles (Synapsida) that ultimately gave rise 



Fig. 35.15. Upper, a small dinosaur, the bird catcher (Ornitholestes), 5 or 6 

 feet in length, that lived 200,000,000 years ago, here represented in the act of 

 catching the first known bird (Archaeopteryx). In such agile animals the two 

 footed pose was finally established along with a carnivorous diet. Lower, a con- 

 temporary dinosaur, the four-footed Tyrannosaurus, of 50 feet total length, and a 

 weight 8 to 10 tons. So far as fossil remains show, this is one of the largest 

 animals that ever lived. Restorations from fossils, painted by C. R. Knight and in 

 the American Museum of Natural History. (Courtesy, Colbert: The Dinosaur 

 Book. New York, American Museum of Natural History, 1945.) 



