Usually, the vertebrae’s large, spool-shaped bodies, the centra, Realistic dinosaur costume are separated from each other by cartilage discs. It is important to take these into account, for if the vertebrae were put together without these spacers then the column would be too short by 10 percent or so. Sometimes articulated backbones were preserved like this, Animatronic dinosaur because the cartilage discs dried up after death and pulled the vertebrae tightly together. The cartilage discs were elastic, and the early galloping lagosuchians still had fairly flexible trunks like the thecodonts’. But the other bipedal predaceous dinosaurs’ vertebral spines were often interconnected by partly ossified ligaments, and they had much smaller rygapophysis on the back trunk vertebrae. Both features restricted the mobility of the trunk, especially the back half of it, yet another adaptation found in birds. Indeed, the back vertebrae of some birds are fused together.
The hip, attached to the spinal column by two sacral vertebrae in paleodinosaurs, also becomes more firmly placed in theropods by four to six such hip vertebrae. walking dinosaur costume So, although the front of the trunk was fairly flexible, drawings showing theropods bending their backs sharply over a victim are incoruect.lr These rigid backs and hips were very unlike the supple bodies of such modern predators as cats and dogs-and they are hard to explain. They could not have been simply for weight support, as they were a feature of even the small, early theropods. Nor were they more effi.cient, since birds have been found to have as rnuch bone mass in their bodies as mammals. We can, however, now see why the theropod neck was so very flexible: it made up for the stiffness of the body.