62 THE ORIGIN OF MAN 



were active forms running upon their hind limbs 

 and with hands and feet armed with increasingly 

 powerful claws and jaws with slightly curved 

 dagger-like teeth, with which they relied for sus- 

 tenance and defense. The Theropoda verged 

 into three lines of descent two of which remained 

 carnivorous and terrestrial in habit, one being a 

 smaller, more agile race preying upon the hum- 

 bler reptiles and possibly upon the birds, the 

 other growing more and more ponderous as time 

 went on. One peculiar feature of their evolution 

 was the arrest of the development of the fore 

 limbs until they became so small as to be abso- 

 lutely useless. The third race which evolved from 

 the theropodan stock and which was named 

 Sauropoda (meaning reptile-footed) had a very 

 brief career. This group is represented by the 

 majestic Brontosaurus, a creature ponderous of 

 body and with a long tapering neck and tail. 

 The teeth being blunted and often somewhat 

 spoon shaped were so ill fitted for any type of 



