File:Bulletin - United States National Museum (1920) (20497063122).jpg

Title: Bulletin - United States National Museum
Identifier: bulletinunitedst1101920unitfo (find matches)
Year: 1877 (1870s)
Authors: United States National Museum; Smithsonian Institution; United States. Dept. of the Interior
Subjects: Science
Publisher: Washington : Smithsonian Institution Press, (etc. ); for sale by the Supt. of Docs. , U. S. Govt Print. Off.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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OSTEOLOGY OF CAENIVOKOTJS DINOSAUKS. 89 On the internal side the dentary is overlain by the splenial and supradentary. Posteriorly the dentary sends back a thin pointed process on the lower border, which laps along the outer side of the angular, ending anterior about the iniddle of the external mandibular foramen. The complete coalescence of the dentary and siu^angular renders the point of their union undetermined, though on the external surface above the external mandibular foramen there is indication of a second lapjaing process of the dentary upon the siu^angular, but of this one can not be sure. On the external surface of the dentary are the usual foramina, which doubt- less served for the transmission of nerves and nutrient blood vessels to the lips. SufraHentary^ (d.p.).—The supradentary in Ceratosaurus, recognized in this genus for the first time, is a long, thin bone, that extends along the upper, inner side of the dentary (fig. 55). It extends nearly the entire length of the dental series and hides from an internal view the greater portion of the dental "rugosae." The upper border of the anterior half of this bone is slightly below the tops of the rugosae, but on the posterior half it rises above them to form the inner parapet of
Text Appearing After Image:
Fig. 55.—Inteenal view of lefteamus of Ceratosaheus nasicoenis Maesh. No. 4735, U.S.N.M. ) NAT. si2E. an, angulab: or, AETICULAR: d, denatey; d.p, supeadentaet; ex.m.f, external mandibulae foramen; par, prearticiilae; sp, splenul; sur, sueangular; 10, root of tenth tooth; 15, indicates position of last alveolus. the alveoli, and in that way it contributes somewhat to the support of the teeth. The anterior end is missiug, but apparently it was pointed and ended just posterior to the most anterior tooth, as shown in figure 55. Hay ^ regarded this element as being the anterior portion of the splenial, but in this he certainly was mistaken, for on examination of the specimen the splenial is plainly seen to overlie this element. In Tyrannosaurus Osborn^ concludes that the supradentary is "apparently of splenial origin, but suturally separated from it." I fail to fixid any evidence to bear out this assertion in the material now at hand. Angular (an.).—In the first restoration of the Ceratosaurus skull by Marsh (pi. 8, fig. 1, Dinosaurs of North America), no attempt was made to differentiate the elements of the posterior hah" of the jaw. Hay was the first to recognize these bones, though liis description of them is very brief. The angular, somewhat dis- placed, is plainly sho^vn on the right ramus (fig. 1, pi. 17). It is a thin, flattened ele- ment that articulates by squamous union vnth the lower median portion of the ' Name proposed by Osbom in 1912 (Mem. Amer. Nat. Hist., vol. 1, p. 5). Lambe in 1904 recognized this same element in Albertosauriis but tailed to give a distinctive name, designating it as the "inner alveolar plate of dentary." (Contrib. to Canadian Paleontology, vol. 3, pt. 3, 1904, pt. 11.) » Proc. U. S. Nat. Mus., vol. 35, 190S, fig. 4. « Mem. Amer. Mus. Nat. ffist., vol. 1, pt. 1, 1912, p. 24.

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