CHORDATA — VERTEBRATA — REPTILES 363 



pounds weight eats 30 pounds of meat per day, while a full 

 grown male lion weighing 500 pounds consumes in the active 

 wild state 40 pounds of meat per day. 



The third branch (Ornithopoda), also herbivorous, had 

 bird-like or tortoise-like horny beaks. Some, as Trachodon 

 from the Upper Cretaceous of the Rocky Mountains, walked 

 upon two feet and were unarmored. Others, including the fol- 

 lowing, walked upon all four feet and were covered with a bony 

 armor. Stegosaurus ungulatus (Figs. 155, 156), from the Upper 

 Jurassic of the Rocky Mountains, was about thirty feet long and 

 weighed at least ten tons. It had probably the smallest brain 

 (about ten pounds) in proportion to its size of any land verte- 

 brate, but to control the huge tail and hind limbs there was a 

 very large expansion of the spinal cord in the region of the hip 

 bones, making a sort of second brain, twenty times larger than 

 that in the head. The animal was protected by numerous 

 small, bony plates embedded in the skin of the head and neck, 

 and by huge, massive, triangular bony plates extending along 

 the middle of the back from the head over two-thirds of the 

 tail, the remaining one-third bearing two or four pairs of large 

 spines. These plates and spines were in life covered by horny 

 sheaths as is shown by their superficial vascular grooves. As 

 the bones are solid the animals doubtless moved very slowly ; 

 this, added to their small head, small blunt teeth and huge size 

 necessitated an abundance of succulent herbage near at hand ; 

 otherwise they would have died of starvation. 



Immediately preceding the extinction of an order or family 

 there is usually a development of bizarre forms, as spinous 

 shells, and twisted cephalopods, representing apparently the 

 remnant of developmental force in that family or order thrown 

 out spasmodically just before, its extinction. Stegosaurus is 

 an example of this among the dinosaurs ; another excellent 

 example is the Upper Cretaceous Triceraiops prorsus, also 

 one of the Ornithopoda (Fig. 157). This quadrupedal, her- 

 bivorous animal with solid bones had a sharp cutting beak, a 



