File:Image from page 46 of "Water reptiles of the past and present" (1914) (14586497837).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: ing reptiles,as we shall see. In some pterodactyls, unlike all other knownanimals, the scapula articulated at its upper end with the backbone,giving a much firmer support for the anterior extremities. Only THE SKELETON OF REPTILES in those reptiles alliedto the ancestors of themammals has thescapula ever had aspine or projection onits dorsal side. Of the two coracoidbones in the originalpectoral girdle theposterior one beganto disappear early andis entirely lost in allreptiles that lived laterthan Triassic times,though it still persistsin the lowest mam-mals, as we have seen.In most later reptilesthe remaining coracoidhas become less firmlyattached to the scapulathan it was in the olderreptiles. It usuallyhas a small foramenpiercing it near themiddle of the upperborder or end, thesupracoracoid fora-men. The clavicle,while more constantamong reptiles thanamong mammals, hasbeen lost in some, theCrocodilia, for in-stance, as also thedinosaurs and ptero-dactyls. The inter-clavicle is more

Text Appearing After Image: 36 WATER REPTILES OF THE PAST AND PRESENT constant in reptiles, a more or less T-shaped bone underlying thecoracoids where they join, or the breast bone; but there were somereptiles that lost it, the dinosaurs and pterodactyls, for instance.In the turtles both the clavicles and the interclavicle form a partof the under shell or plastron.

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