Back at Yale, Ostrom constructed an overwhelming argu ment to prove his case. (animatronic dinosaur rides)Between Archaeopteryx and Deinonychus the long bony fingers were not the only things identical. So was nearly every detail of their shoulder, hip, thigh, and ankle. As a conse-quence, questions about dinosaurs which had long baffled the scholars could be solved when Archaeopteryx was used as a stan-dard of comparison. Deinonychus, for example, had had a strange lower shoulder-blade bone (coracoid), unique among dinosaurs because of its great depth from shoulder socket to breastbone. But Archaeopteryx had had a coracoid of the same deep pattern as Deinonychus. Clearly both the bird and the dinosaur had evolved the unusual shape to increase the size of their breast muscles. Deinonychus had had a peculiar upper hip bone (ilium) compared to other predatory dinosaurs, but Arcbaeopteryx exhibited the same peculiarities. And in its wrist Deinonycbus’s similarities to birds were nothing short of astounding.
The wrist bones and hand the structures that had first caught John Ostrom’s attention were, in fact, the single most persuasive part of his argument. The wrists of primitive reptiles were simple devices, merely a flexible mosaic of squarish bones held together by ligaments. When a primitive reptile pressed its wrist against the ground, the mosaic of bones could bend or twist but couldn’t pro-duce any precisely controlled movement. Arcbaeopteryx and all modern birds are different. The joint surfaces of wrist bones are complexly curved, and the large central bone has an elegantly designed joint surface of semicircular shape that guides the animal’s hand in a precisely controlled flexing movement. (dinosaur facotyr)Prior to Ostrom’s discoveries, most scientists tended to believe that the bird type of wrist had evolved rather suddenly, in the first true birds. Neither primitive dinosaurs nor the false-croc reptiles Heilmann favored as the ancestors of birds possessed anything like the bird type of wrist. But Ostrom found that Deinonycbus’s wrist bones were identical to those of Arcbaeopteryx, and that Deinonycbus’s wrist would therefore deliver the very same sort of precise flexing movement in the entire set of fingers. (life size dinosaur for sale)Moreover, the long fingers so distinctively characteristic of Deinonycbus had been designed identically in Arcbaeopteryx. Both Arcbaeopteryx and the dinosaur had had three fingers only not the five found in primitive dinosaurs. And the proportions of the fingers had been the same: A short, stout thumb and two longer outer fingers, with the outer-most of the three very slender, bowed outward, and closely bound by ligaments to the middle finger. This unique pattern can still be recognized in a modern bird’s wing; the three fingers are all firmly fused together in an adult bird, but in an unhatched chick, the bones are not yet fused. In a chick the separate wrist and hand bones are clearly discerned, exactly as they had been in Deinonycbus and Arcbaeopteryx.