File:Image from page 35 of "Water reptiles of the past and present" (1914) (14792838253).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: aretwo openings on each side, called the supratemporal and lateraltemporal vacuities. In another still larger group there is a singlevacuity on each side, all members of which it has been thought weremarkedly related to each other. Some of these, the lizards, snakes,and mosasaurs, the ichthyosaurs, and probably the proganosaurs. 24 WATER REPTILES OF THE PAST AND PRESENT have the single opening high up on the side, correspondingapparently to the supratemporal vacuity of the double-archedforms, as those with two openings are called. Many others, how-ever, like the whole order Therapsida and the Theromorpha, havethe single opening lower down and bounded differently; theirrelationships are doubtful, since it is very much of a question howthe single opening has arisen. There have been many theoriesto account for the origin of the temporal vacuities, but all are yetspeculations. Notwithstanding these doubts, which more recentdiscoveries have intensified, there can be none that the structure

Text Appearing After Image: Fig. 8.—Sphenodon (tuatera). Skull from side and above: pm, premaxilla;n, nasal; prf, prefrontal; /, frontal; pf, postfrontal; p, parietal; po, postorbital;sq, squamosal; m, maxilla; j, jugal; qj, quadratojugal; q, quadrate; c, coronoid;sa, surangular; art, articular; pa, prearticular; d, dentary; an, angular. of this region of the skull offers important and reliable charactersfor the classification of the reptiles into the larger groups, but,unfortunately, we are very uncertain yet as to what this classi-fication should be. We are confident that all those reptiles havingtwo temporal vacuities on each side are related to each other; weare yet very much in doubt as to the classification of all otherreptiles, or at least all others having-only a single temporal vacuityon each side. Better evidences of relationships, or the absence of relation-ships, are offered by the presence of certain bones in the skullsin some orders that are lost in others, since it may be accepted as THE SKELETO

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