. The origin and evolution of life, on the theory of action, reaction and interaction of energy. J Fig. 99. Primitive Iguaxodont Camptosaurus from the Upper Jurassic of swift bipedal form was contemporary with the giant sauropod Apatosaunis and thelighter-bodied Diplodocus. These iguanodonts were defenseless and dependent whollyon alertness and speed, or perhaps on resort to the water, for escape from their were the prey of AUosaiirus (see Fig. 91). Mounted specimen in the AmericanMuseum of Natural History. entirely different stock of bipedal herbivorous dinosaurs inw
. The origin and evolution of life, on the theory of action, reaction and interaction of energy. J Fig. 99. Primitive Iguaxodont Camptosaurus from the Upper Jurassic of swift bipedal form was contemporary with the giant sauropod Apatosaunis and thelighter-bodied Diplodocus. These iguanodonts were defenseless and dependent whollyon alertness and speed, or perhaps on resort to the water, for escape from their were the prey of AUosaiirus (see Fig. 91). Mounted specimen in the AmericanMuseum of Natural History. entirely different stock of bipedal herbivorous dinosaurs inwhich the pelvis is bird-like (Ornithischia, Seeley). Theseanimals may be traced back (von Huene) to the TriassicNaosaurus. The front of the jaws at an early stage lost theteeth and developed a horny sheath or beak like that of thebirds, within which a new bone (predentary) evolves, giving tothis order the name Predentata. Entirely defenseless at thisstage {Camptosaurus), these relatively small, bipedal types 222 THE ORIGIN AND EVOLUTION OF LIFE. Fig. loo. A Pair of Upper Cretaceous Iguano- DONTS FROM MONTANA. After a lapse of 500,000 years of Cretaceous time theCamptosaurus (Fig. gg) evolved into the giant duck-billed dinosaur Trachodon, described by Leidy andCope from the Upper Cretaceous of New Jersey andDakota. Two skeletons of Trachodon annedens (upper) discoveredin Montana, as mounted in the American Museum ofNatural History, and restoration of the same (lower)by Osborn and Knight. (Compare Fig. 74.) spread all over thenorthern hemisphereand attained an extra-ordinary adaptive radi-ation in the river- andshore-living duck-bill dinosaurs, theiguanodonts of the Cre-taceous Epoch (). The adaptiveradiation of these ani-mals has only recentlybeen fully determined;it led into three greattypes of body form, allunarmored. First, theless specialized typeswhich retain more orless the body structureof the earlier Jurassicforms and the famousiguanodont of Bernis-sart, Belgium.
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