File:Image from page 61 of "Water reptiles of the past and present" (1914) (14769819511).jpg

Identifier: waterreptilesofp1914will Title: Water reptiles of the past and present Year: 1914 (1910s) Authors: Williston, Samuel Wendell, 1851-1918 Subjects: Aquatic reptiles Publisher: Chicago, Ill., The University of Chicago Press Contributing Library: Boston Public Library Digitizing Sponsor: Boston Public Library

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Text Appearing Before Image: Fig. 26.—Captorhinus, a cotylosaurreptile from Texas, about one-fourthnatural size. 50 WATER REPTILES OF THE PAST AND PRESENT hundred species of six or seven groups, and at least two orders havebeen described. Of these the Cotylosauria are the continuationof the American order, but include more specialized forms, thePareiasauria and the Procolophonia, all of them, like the moreprimitive American forms, characterized by the imperforatetemporal region. The Therapsida, likewise, seem to be the con-tinuation of the American Theromorpha, so closely allied to themthat it is difficult to draw a distinguishing line between them.On the other hand, these African reptiles merge through theTheriodontia into the mammals in the Triassic. They are all

Text Appearing After Image: Fig. 27.—Restoration of Labidosaurus, a cotylosaur reptile from Texas, aboutthree feet long. terrestrial, crawling reptiles, except a few which are describedon a later page under the Anomodontia. The records of the lower part of the Triassic period are scantyeverywhere in the world, save perhaps in Africa. Before the closeof the period, however, probably every important group of cold-blooded air-breathing animals had made its appearance in geologicalhistory, if we except the snakes; even the mammals had appeared,and possibly the birds. The Cotylosauria, Theromorpha, andTherapsida disappeared, the latter giving birth to the mammals;the nothosaurs and plesiosaurs, the ichthyosaurs, dinosaurs, croco-diles, phytosaurs, rhynchocephalians, lizards, and turtles have allleft records of their existence in Upper Triassic rocks; and thepterodactyls had also, in all probability, begun their career,though none is surely known till the Jurassic. THE AGE OF REPTILES 51 During Jurassic times all th

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