126 Biology in America 



Plains area of the West. In the early Mesozoic rocks of this 

 region are found some of the most extensive dinosaur remains 

 throughout the world, although these are of virtually world- 

 wide distribution. And here too has been the happy hunting 

 ground of the palaeontologist, whose labors have revealed to 

 us the life of the long ago. 



In size the dinosaurs ranged from little fellows about a 

 foot or two long to enormous beasts, veritable Goliaths among 

 animals. The largest of all was Brontosaurus, the thunder 

 lizard, who reached a length of sixty feet, and stood fourteen 

 feet high, with a thigh bone the height of a man. Many of 

 them were armed with great knife-like plates and spines upon 



DINOSAUR TRACKS 

 Courtesy of the American Museum of Natural History. 



the back and tail. Among these were the stegosaurs or 

 armored lizards, the largest of whose plates were two feet in 

 height and length, while near the end of the powerful tail, 

 eight or ten feet long, projected two pairs of vicious spines 

 nearly three feet long. The three-horned dinosaur, Tricer- 

 atops, who some millions cf years ago inhabited what are now 

 the plains of the Dakotas, Wyoming, Montana and Colorado, 

 bore a horn over either eye and one on his snout, like the 

 horn of a rhinoceros, and a great fringed shield upon his 

 neck; while many another was equipped with armor more 

 bizarre perhaps than practical in the battle of life. Many 

 however were naked, so that as a protective adaptation these 

 various plates and spines seem to have had but doubtful value. 



