File:Image from page 124 of "Water reptiles of the past and present" (1914) (14770658874).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

View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book

Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image: ial reptiles. They have, as an order, so isolated a position,are so widely separated from all other reptiles in structure, that theyhave long been a puzzle to paleontologists. Like the whales andother cetaceans among mammals, we know the ichthyosaurs wellin the plenitude of their power and the fulness of their development,but have yet only an imperfect knowledge of their earlier history,and none whatever of their earliest. However, as will be seenfarther on, the recent discoveries by Merriam have shed much lighton some of the stages of their evolution. So nearly perfectly wereall the later ichthyosaurs adapted to their life in the water that itwas believed by nearly all paleontologists until about a score of years ICHTHYOSAURIA 3 ago that they had descended directly from fishes. But this beliefhas been quite abandoned by all, not only because the recent dis-coveries of the earlier ichthyosaurs have demonstrated a positiveincrease in the aquatic adaptations of the later forms, but also

Text Appearing After Image: Fig. 53.—Baptanodon (Ophthalmosaurus). Skull from the side, from above, andfrom below (after Gilmore): ang, angular; bs, basisphenoid; d, dentary; fr, frontal;f, jugal; la, lacrimal; mx, maxilla; na, nasal; oc, occipital condyle; p, palatine; pa,parietal; pm, premaxilla; po, postorbital; ps, parasphenoid; pt, pterygoid; pf, pre-frontal; sa, surangular; sp, splenial; sq, squamosal; st, supratemporal; q, quadrate;qj, quadratojugal. because a double origin of any type of animal life is quite out ofaccord with all known facts and principles of paleontology. It isquite possible for animals, in becoming adapted to peculiar environ-mental and food conditions, to acquire certain resemblances to ii4 WATER REPTILES OF THE PAST AND PRESENT other animals, but quite impossible for them to acquire their actualstructure. The ichthyosaurs are true reptiles, and all reptilesmust have had a common origin. We are sometimes in doubt, however, as to whether charactersresembling those of other animals ar

Note About Images