File:Image from page 95 of "Water reptiles of the past and present" (1914) (14586519637).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. 36.—Pelvic girdle from above of Trinacromerum osborni, an Upper Cretaceousplesiosaur: p, pubis; is, ischium; il, ilium. Many of the characteristics of the limbs of the plesiosaurs arepeculiar to themselves; others they had in common with other 84 WATER REPTILES OF THE PAST AND PRESENT aquatic reptiles and mammals. The paddles resemble those of theichthyosaurs more nearly than those of any other reptile, and itwas doubtless this superficial resemblance which so long deceivedthe early anatomists as to the affinities of the two orders. Unlikeall other aquatic animals, however, the plesiosaurs have the hindlimbs nearly or quite as large as the front ones, and they doubtlesswere equally effective in function. The humerus and femur arealways elongate, though broad and massive. In no other aquaticanimals, save the marine turtles, do we find these bones relatively

Text Appearing After Image: Fig. 37.—Pelvic girdle of Elasmosaurus: p, pubis; is, ischium; il, ilium so long and strong; they are very short in the cetaceans, the sire-nians, the ichthyosaurs, mosasaurs, thalattosaurs, and the marinecrocodiles, in front at least. The strong muscular rugosities ofthe plesiosaurian bones are very suggestive of powerful swimmingmuscles. The bones of the forearms and legs, the wrists and ankles areall polygonal platelets of bones, closely articulating with each other.The finger and toe bones have a more elongated, hour-glass shapethan those of the ichthyosaurs, resembling more nearly those of the SAUROPTERYGIA 85 mosasaurs, indicating a greater flexibility than the ichthyosaurspossessed. The ichthyosaur paddles must have been quite likethe fins of fishes in function, while doubtless those of the plesiosaurswere capable of a more varied use, as indeed was required of them.Their articulation with the trunk was more of a ball-and-socket

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