. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 182 S. \V. WILLISTON. might be supposed to be the prosquamosal, but in the excellent skulls of four genera of these animals which I have examined there is positively no such separate element present, nor was there any recognizable prosquamosal present in the skulls de- scribed by Andrews. Nor has such an element ever been recog- nized in the Nothosauria. I am aware that Kokenl has suspected the presence of such an element in one specimen of a nothosaur, but his evidence was very doubtful and has not been confirmed. I am conf
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 182 S. \V. WILLISTON. might be supposed to be the prosquamosal, but in the excellent skulls of four genera of these animals which I have examined there is positively no such separate element present, nor was there any recognizable prosquamosal present in the skulls de- scribed by Andrews. Nor has such an element ever been recog- nized in the Nothosauria. I am aware that Kokenl has suspected the presence of such an element in one specimen of a nothosaur, but his evidence was very doubtful and has not been confirmed. I am confident that the true squamosal in these groups, as in the cotylosaurs and turtles, articulates directly with the post-. FiG. 17. Ichthyosaurus, after Owen. orbital and jugal, without the intervention of any other element, and that the prosquamosal is wanting, not fused with adjoining bones ; nor is there any certain evidence of the presence of the quadratojugal in any of these reptiles. In certain plesiosaurs I have found and figured what I believed to be a distinct ossifica- tion--a small, perhaps rudimentary one — that I took to be the quadratojugal. But I have never been able to trace it out, and no other observer has ever distinguished this element in the Sauropterygia. In the Anomodontia no such element has been certainly found, and, since we have the best of reason for believ- ing that the anomodonts and theriodonts are closely related to the ancestors of both the nothosaurs and the plesiosaurs, we can hardly expect to find the bone distinct in these latter forms. 1 Zeitschr. Deutsch. Geolog. Gesellsch., XLV., 1893 ; p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952;
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
