Occurrence of Cretaceous Reptiles in the Moreno Shales of the Southern Coast Ranges, California

Abstract

Recently, S. P. Welles called attention to a plesiosaur from the Upper Cretaceous of the San Joaquin Valley, California, and on the basis of its skeletal characters, long neck and short head, referred this sauropterygian to the family Elasmosauridae [1]. During the past summer, field parties from the California Institute of Technology explored the Moreno formation as exposed in the Panoche Hills, northwestern Fresno County. Our attention was drawn specifically to this region by the discovery of reptilian remains by Robert T. White of the Barnsdall Oil Company, The materials found by Mr. White proved to be on excavation a shoulder girdle, one flipper, a series of sixty or more vertebrae and remains of the posterior part of the skull and jaws of a plesiosaur. Apparently the marine reptile represented by these remains possesses several of the characters noted by Welles in the plesiosaur found approximately five miles farther north in the Panoche Hills, although the second specimen is distinctly smaller than the first. Further search in the region where the second plesiosaur was found revealed the presence of two other types of reptiles. These represent mosasaurs and an hadrosaurian dinosaur. Both types are of interest, and the latter particularly, because for many years no record has been made of the presence of these groups in Cretaceous deposits of. the Pacific Coast of North America, although they are not uncommon in certain horizons of the Cretaceous found elsewhere on the North American continent. Discovery of these reptiles in this far western area is of considerable scientific interest and possesses great significance since among other facts derived from the study of the remains as well as of the occurrence, light may be thrown not only on the age relationships of the Moreno but also upon the conditions under which at least certain portions of the formation accumulated.