OCR Text |
Show 1 9 0 5 .] ON THE SUPPOSED CLAVICLE OF DIPLODOCUS. 2 8 9 9. Remarks on the supposed Clavicle of the Sauropodous Dinosaur D ip lo d o c u s . B y F r a n c i s , B a r o n N o p c s a , Ph.D.* [Received June 6, 1905.] (Text-figures 16-49.) It is still uncertain whether the extinct Dinosauria possessed clavicles. Considering the close relationship existing between these reptiles, the Rhynchocephalians, Parasuchians, and Birds-this last relationship being shown by the continuous tendency of Dinosaurs to specialize on most different occasions in bird-like manner-one is at first naturally induced to believe that in Dinosaurs clavicles were present; but, as a matter of fact, bone after bone supposed to represent this element has had to be removed from this position. Hitherto only the family Ornitliopodidte is known to possess, in addition to scapula and coracoid, a curious further element in the shoulder-girdle, which was called clavicula, but may quite as well form only a part of the sternum (this double element being in one case united in the middle by bony matter). No other Saurischian or Orthopodous Dinosaur shows a clavicular ossification. It is true that in the Sauropoda, besides scapula and coracoid, one or two flat bones are always present in the scapular region of the body : these, however, do not represent claviculee, but may with certainty be determined as ossifications of the sternum. The discovery, therefore, of what may be called a supernumerary bone besides the sternal plates in two of the several Diploclocus skeletons known to science proves to be of quite exceptional interest. Hatcher, in his important Monographs of the Diplodocus skeletons Nos. 84 and 662 of the Carnegie Museum, describes this element as follows :-" Throughout the greater portion of its length it is circular in cross-section, it is bifid at one extremity and slightly expanded at the other. It is strongly curved, especially toward the bifid extremity. It is asymmetrical." In a more complete specimen (No. 662) than the former (84) it is " somewhat expanded and spatulate; the flattened extremity presents a slightly rugose surface, as though it had been imbedded in cartilaginous or muscular tissue, and this together with the bifid nature of the other extremity has suggested the possibility that the bone might be an os penis." After the description of this bone, however, its asymmetry is regarded by this eminent paleontologist as a weighty argument against its being an os penis, and therefore its identification with the clavicula is advocated. * C om m u n ic a t e d b y D r . A. S m i t h W o o d w a r d , F.R.S., F.Z.S. P roc. Z ool . S oc.-1905, V o l . II. No. XIX. 19 |