HVBITS AND MANNER OF LIFE 21 



saurs of the Jura, but, in part at least, from small and little known forms, o| more upland adapta 

 don, which had been much more highly specialized for dry land life than any ol the Jurassic swamp 

 dwellers, and had readapted themselves to the forest and swamp environment of the later Creta 

 ceous.' H As heritages from this upland phase ill their evolutionary history, Matthew stresses particu- 

 larly the efficient grinding dentition and the compact feet with depressed hoofs, which characterize- 

 both the trachodons and ceratopsians, for these characters when found in modern mammals are 

 especially associated with an upland habitat. As further evidence for this upland stage, he cites the 

 rarity of very young animals among the thousands of dinosaurs which have been unearthed in the 

 principal quarries. In Protoceroto-ps, all stages from the egg to the old adult are known, but in 

 America I know of but a single form which can really be called adolescent and that is Gilmore's 

 Brac/iycenirops* All of the rest are fully adult, although not all are aged individuals. Hence, 

 Matthew argues that the laying of eggs or bringing forth of young was done elsewhere than in the 

 adult environment, probably in the upland regions where the periods of infancy and adolescence were 

 passed, the creatures coming to the swamps on maturity when increasing size made the amphibious 

 environment more suitable. It is well known that many animals today return periodically to their 

 own birthplace to produce their offspring, but the final significance lies in the fact that the breeding 

 or egg-laying place would be presumptively the ancestral habitat of the race. 



While the trachodons, with their webbed feet and laterally compressed swimming tail, arc- 

 clearly splendidly adapted to an amphibious life, fully as much so as a modern crocodile, I cannot 

 see any character or group of characters in the ceratopsians which can be interpreted as in any sense 

 aquatic in their adaptation. On the contrary, the low-carried head with the nostrils near the ground, 

 the cumbersome limbs, and the relatively short tail as compared with that of other dinosaurs, all 

 point to a terrestrial manner of life. Swampy areas, where the ground was sufficiently firm to bear 

 their weight without miring, and perhaps an occasional water hole would be visited but never the 

 actual aquatic environment. I would visualize their manner of life as somewhat similar to that of 

 a modern browsing rhinoceros, which they resemble superficially in a number of ways, but I doubt 

 whether submergence would be desirable either for coolness or for ridding the body of parasites, for 

 modern reptiles bask in a scorching heat and it is difficult to imagine ticks or insect pests having 

 any effect on the thoroughly protected hide of a ceratopsian. 



FEEDING HABITS 



There is no ambiguity about the mouth armament of a ceratopsian. It is clearly that of an 

 herbivorous animal and is not in any sense fitted for the rending of prey. Anteriorly, there is a 

 laterally compressed beak, while in the rear of the mouth, there is a splendid battery of successional 

 teeth comparable to those of the trachodons; although the individual teeth are larger, and conse- 

 quently fewer in number, and their mode of succession is different, they are fully as efficient. There 

 is evidence that the masticating area of the jaws was enclosed by powerful muscular cheeks, formed 

 largely of the masseter muscles, and the well -developed coronoid points to equally powerful temporal 

 muscles. Altogether, the mouth, with its activating tissues, was fully as efficient as that of a modern 

 rhinoceros, with this advantage, that the endless succession of teeth gave no limit to the expecta- 

 tion of life as compared with the very definite limit of a modern mammal whose permanent teeth, 

 once worn out, cannot be replenished. The jaw movement was a vertical or chopping one through an 

 arc the center of which lay in the articulation, with no indication either of lateral sway or of fore 

 and aft motion; and the teeth met, not as in a modern ungulate with the horizontal surface of the 

 crowns in contact, but shearing past each other so that the occluding surfaces were vertical, on the 

 inside of the lower teeth and outside of the upper. They were in effect like two converging pair 

 shears, one on either side of the mouth. Hence their mastication was not a grinding one, but a shear - 



4 Matthew, W. D., 1915, p. 278. 



5 Gilmorc, C. W., 1922, B. 



