EVOLUTION OF THE VERTEBRATES 



153 



cious bipedal giants which must have been a terror to the other 

 inhabitants of the earth. The pterosaurs flew by means of folds 

 of skin extending from the hind limb to one enormously elongated 

 digit of the fore limb. In the cjmodonts, or dog-toothed reptiles, 

 we find the probable ancestors of the mammals, and in some an- 



FiG. 85. — Group of Mesozoic reptiles. A, long-necked plesiosaur, Elasmo- 

 saurus; B, short-necked plesiosaur, Trinncromerion; C, ichthj'osaur, Bap- 

 tanodnn; D, pterodactyl; E, ostrich dinosaur, Slrulhiomimus; F, carnivorous 

 dinosaur, Tyrannosaurus; G, giant herbivorous dinosaur, Brachiosaurus; 

 H, hooded duck-bill dinosaur, Corythosaurus. (From Newman, after 

 Osborn.) 



