File:The dinosaur book - the ruling reptiles and their relatives (1951) (19777827894).jpg

Title: The dinosaur book : the ruling reptiles and their relatives
Identifier: bookruli00colb (find matches)
Year: 1951 (1950s)
Authors: Colbert, Edwin H. (Edwin Harris), 1905-2001; Knight, Charles Robert, 1874-1953; American Museum of Natural History
Subjects: Dinosaurs; Reptiles, Fossil
Publisher: New York : Published for the American Museum of Natural History by McGraw-Hill
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: IMLS / LSTA / METRO

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Allosaurus and Tyrannosaurus, had widely gaping mouths armed with huge, bladelike teeth. Only in the toothless "ostrich dino- saurs" such as Struthlomimus was there a departure from this primitive or ancestral carnivorous diet among the theropods. Most of the dinosaurs were, however, herbivorous, living upon green plants. In this category, we find the sauropods among the Saurischia and all of the dinosaurs belonging to the order Ornithischia. Con- sequently there were various adaptations for eating plant food in these animals. In the giant sauropods dental adaptation seemed to be mainly a process of limiting the teeth to the front of the jaws and trans- forming them into rather weak pegs. How such teeth, mounted in such small jaws, could serve to tear off enough leaves from their stems to keep these huge dinosaurs going, is a problem that baffles the imagina- tion, yet the evidence is there and cannot be refuted. These dinosaurs did live, and very successfully too, for many millions of vears. In the ornithischians the teeth were re- stricted to the sides of the jaws, the front of the jaw being transformed into a sort of a beak, as mentioned above, consisting of the premaxillary bones in the upper jaw and of a new element, the predentary bone, in the lower jaw. This sharp, birdlike beak must have served these dinosaurs for the purpose of tearing green leaves away from their stems. When it came to the process of chopping and chewing the plant food into digestible bits, the ornithischians were admirably provided with dental batteries of consider- able complexity. In the primitive campto- saurs there was a row of fluted teeth on either side of each jaw, which when worn maintained sharp edges that would serve to chop the food by a scissor-like motion of the jaws. Modifications of these teeth occurred in the armored dinosaurs and in the cera- topsians or horned dinosaurs, but it was in the aquatic hadrosaurs that the dental bat- tery attained its most specialized form. There was in these dinosaurs a tremendous increase in the number of the teeth so that instead of a relatively few teeth in each jaw, above and below, there were in each jaw some 500 teeth. Thus there was a total of about 2000 teeth in the mouth of a tvpical duck-billed dinosaur. These teeth, which were small and rather lozenge- shaped, were arranged in several closely packed rows. When worn, the overlapping surfaces of the teeth formed a rough pave- ment that served to grind the food, mill- fashion, into a pulpy mass. As in a well- organized army, there was a large number /
Text Appearing After Image:
^ In the Saurisi-hia, hs illustrated by Allosaurus, the hinge of the jaw is approximately on a line with the tooth sockets. The jaws were closed by a scissors action, with the upper and lower teeth sliding past each other 88

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