1 46 POPULAR SCIENCE MONTHLY. 



wide variation and distribution in the Jurassic implies an ancestry in 

 the earlier period, and also that their footprints on the Triassic sand- 

 stones are unmistakable. 



The more primitive herbivores resemble their carnivorous allies in 

 general contour and in mode of progression, though differing in certain 

 internal characters and in the teeth, these being necessarily changed 

 to enable their owner to chop or grind up the plants upon which it 

 lived. The rear part of the jaws became, in the later forms, veritable 

 magazines of teeth, the latter replacing one another in vertical succes- 



-»*£*' 



Beach with Tide Mark and the Tracks of an Herbivorous Dinosaur going 



down toward the Water. 



Photographed f'roin a slab in the Amherst College Museum. 



si on, a new one being always ready to take the place of one lost or 

 worn out in service. The front part of the mouth bore a few teeth 

 in the earlier types, but these soon gave way to a horny upper and 

 lower beak, turtle-like in aspect, probably used for cropping succulent 

 herbage. 



The hind feet were still very bird-like, especially in the less special- 

 ized forms, but with blunted claws, while the hand always retained its 

 five fingered condition with short rounded nails. The fore limbs 

 could always be used for the support of the forward parts of the body, 

 though perhaps not always for food gathering. It is extremely doubt- 

 ful whether any of the earlier plant feeders ever walked on all fours, 

 though in the later forms, owing to the great weight of armament 

 which they carried, a four-footed gait was rendered necessary. The 

 herbivorous dinosaurs proved a more plastic race than their carnivorous 

 brethren, and towards the close of their career there arose among them 

 the remarkable types, already alluded to, which marked the decadence 

 of the group. 



In the footprint fauna the herbivores were all true bipeds, but did 

 occasionally impress the hand, including thus all the footprints of the 

 second or occasionally quadrupedal group, and probably some of the 

 first as well, though this is open to question. 



The footprints give us thus our first recorded evidence of herbivorous 

 dinosaurs in the Triassic, which will some day probably be verified 

 by the finding of their bones. 



