The ostrich is one animal that has such limbs, and of course it is a superb runner.Walking dinosaur costume So do theropods, which are themselves ostrich-like in most respects of their design. This fact has long been recognized to be true of the smaller theropods, especially the “ostrich-mimic” ornithomimids. It is less often noticed but equally true not only of the small tyrannosaurs, but of TJnannoscurus rex and the other big theropods as well.
The ostrich-mimics and tyrannosaurs show this in a remarkable way. ostrich-mimics and tyrannosaurs of increasing size are compared at the same scale. Mechanical dinosaur Because they lived in different ways, they differ in the head, neck, and forelimb. Realistic dinosaur costume But, from 150 kg to 6 or more tonnes they maintain essentially the same birdlike form in the trunk, tail, and most especially the hind limbs. The hip’s ilial bone is big, long and rectangular. The femur is robust and curved-even more in t-rex than in ostrichmimics!- and as explained in Chapter 4, the knee joints were always hrghly flexed. Fibulas are substantially reduced at the lower end. realistic walking dinosaur costume The foot is long and very compressed, with the upper half of the central metatarsal almost pinched out of existence. Indeed, the constancy of design in the ostrich-mimics and tyrannosaurs is extraordinary. Only the proportions and a few details change: tyrannosaurs retain a small inner toe and slightly less reduced fibula in the shank, while shank and foot become relatively shorter in the bigger species. The latter is a consequence of elastic similarity and should not affect performance much; it does not in ungulates. Even with these minor differences, no other animal group shows so unchangrng a design over this size range. The retention of a flexed knee in Tlronnosourus rex is a really astonishing adaptation; it is as highly flexed as those of gazelles, horses, and ostriches!