File:Image from page 96 of "Water reptiles of the past and present" (1914) (14772665182).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. 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

Text Appearing After Image: 4WW? iffl Fig. 38.—Paddles of Plesiosaurs: A, right hind paddle of Thaumatosaurus, afterFraas; B, right hind paddle of Trinacromerum; C, right front paddle of same indi-vidual; /, femur; fb, fibula; t, tibia; h, humerus; r, radius; u, ulna. joint than in the other reptiles, showing possibility of considerablerotation on the long axis, and an antero-posterior propelling action.The paddles were certainly more powerful than those of any otheraquatic air-breathing animals. There were no additional digits,all plesiosaurs having neither more nor less than five in each handand foot. Hyperphalangy was sometimes carried to an excessive 86 WATER REPTILES OF THE PAST AND PRESENT degree, some digits of some species having as many as twenty-fourbones, a larger number than has been observed in any other air-breathing vertebrate.

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