Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...was described by Merriam1 in 1906 as the type of the genus Omphalosaurus. In the absence of complete material it was not possible to determine definitely the relationships of the genus, and it may be placed tentatively in a distinct order, the Omphalosauria. So far as known the animal is a short-headed form, presumably of the synapsidan type. The structure of the palate and the mandible are not unlike that in the plesiosaurs, while other characteristics point toward the rhynchocephalian type. One of the remarkable features of this specimen is found in the nature of the dentition. The dentary elements are set with several rows of teeth, the crowns of which are nearly circular in cross-section, and dome-like in elevation. Therejire at least three rows of teeth on the dentary, with the presumption that many more rows may have been present. The surface of the dentigerous area of the mandible was evidently strongly convex. The nature of the dentition suggests i Merriam, J. C, Univ. Calif. Publ. Bull. Dept. Geol., vol 5, p. 76, 1906. that of certain fishes, while characters of the skull are unquestionably reptilian. Since the publication of the original description of this form Wiman2 has described from Spitzbergen a number of specimens which he refers to the ichthyosaurs, but which are interpreted by Merriam3 as probably representing omphalosaurians. The specimens obtained by Wiman occurred in beds which are considered as representing the Middle Triassic, and the saurian fauna is in general quite similar to that of the Middle Triassic of the West Humboldt Range, in which the type specimen of Omphalosaurus was found. EVIDENCE PRESENTED BY NEW MATERIAL In the material most recently obtained from the Middle Triassic of Nevada there are two...