File:Bulletin (1969) (20233433418).jpg

Title: Bulletin
Identifier: bulletin30peab (find matches)
Year: 1969 (1960s)
Authors: Peabody Museum of Natural History
Subjects: Natural history; Natuurlijke historie
Publisher: New Haven : The Museum
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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FIG. 52. Probable ventral "ribs" of Deinonychus antirrhopus; true abdominal or sternal ribs (A and B) (YPM 5246) and segments of gastralia (C, D and E) (YPM 5247), A is considered a lateral segment and B the sternal segment of a sternal rib. C and D illustrate a medial segment of a gastralia "rib" in ventral (C) and dorsal (D) views. E is interpreted as a probable lateral seg- ment of a gastralia "rib" in ventral view. Articular scars are designated as "a." flattened rods with expanded articular surfaces at each end (Fig. 52A and B), and 2) curved, tapered rods with appositional or articular scars on one or two sides, but with no evidence of terminal articulations (Fig. 52C, D and E). The former are believed to be fully ossified sternal ribs and the latter gastralia. Osbom (1906) in his description of Tyrannosaurus, was the first to record the occurrence of "abdominal ribs" in theropodous dinosaurs. But the struc- tures described (see his fig. 12) are almost certainly gastralia and not ventral extensions of the dorsal ribs. This is indicated by the overlapping, rather than end-to-end, contact of left and right elements, and by their asymmetrical form. The gastralia of Tyrannosaurus appear to have consisted of a series of long, tapered, lateral elements, some of which co-ossified into V-shaped, asymmetrical median bones. The lateral elements probably occurred in pairs, apparently not mirror images of each other, and were joined by overlapping contact at the mid-line. Similar abdominal ossifications were reported by Lambe (1917) in Gorgo- saurus and by Parks (1928) in Albertosaurus. Lambe and Parks also referred to these as "abdominal ribs," but again they appear to be gastralia. Lambe reconstructed the series as extending from the sternum to the pubes and con- sisting of paired median ventral bones overlapping at the mid-line, and short, tapered lateral bones overlapping the lateral extremities of the previous ele- ment. He also described two fragmentary bones that appear to be co-ossified left and right median elements (as in Tyrannosaurus), which he interpreted as the first and last abdominal ribs (Lambe, 1917: fig. 27). Osbom (1917) also described "sternal ribs" in Struthiomimus (= Ornitho-

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