File:Image from page 171 of "Water reptiles of the past and present" (1914) (14750046586).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: ers except the ichthyosaurs and cetaceans. Thesacrum had entirely lost its function as a support to the pelvisand had disappeared, that is, the vertebrae composing it had become 160 WATER REPTILES OF THE PAST AND PRESENT quite like the adjacent ones, by the loss of the ribs connecting themwith the ilium. The small pelvis was suspended loosely in thewalls of the abdomen, or at the most was feebly connected witha single vertebra by ligaments. It was entirely useless as a supportfor the legs. The mosasaurs could not possibly have raised theirbodies from the ground while on land. It is well known that theland lizards and the crocodiles raise their bodies free from the groundwhile running or walking; none drags its body over the surface. In several instances complete or nearly complete skeletons ofmosasaurs have been discovered with the different bones nearlyall in the positions and relations they had after the decompositionof the flesh, together with the carbonized remains of the skin and

Text Appearing After Image: Fig. 78.—Photograph of carbonized remains of scales of Tylosaurus, natural size impressions of the investing scales and membranes. The natureof the body covering is therefore known with certainty from nearlyall parts of the body. The body everywhere, save on the mem-brane between the fingers and toes, and perhaps on the top of theskull, was covered with small overlapping scales, very much likethose of the monitors. These scales, however, were small andsmooth in comparison with the size of the animals, those of amosasaur twenty feet in length being almost precisely the sizeof those of a monitor six feet long. The top of the skull seems tohave been covered with horny plates, as in most lizards. In oneinstance parallel dark bars, obliquely placed, and of narrow width,formed by carbonized pigment, were observed by the writer. Ashas been stated, in some instances fish bones and fish scales have SQUAMATA 161 been observed among the fossilized stomach contents, and it isquite certain that

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