In 1986, Robert Bakker suggested that the theropod skull was just loosely built, and could “give” a lot as big chunks of meat were swallowed. Walking dinosaur costume In this simple system, the cheeks and the tooth-bearing jarvbones met the skull roof along what is in effect . a skull-long hinge joint. At the sarne time, the tips of the lower jaw could pivot upon one another. Figure 4-s shows how all this looseness would allow the jaws to bow outward. In acidition, there may have been a hinge in the skull roof that allowed the snout to be depressed or lifted relative to the rest of the skull. Birds and hzards can do this, but whether this feature really existed in predatory dinosaurs, and how it might have worked, is much less certain.
one extra head joint is known to have existed in the advanced avetheropod’s lower jaw. In primitive predatory dinosaurs the big tooth-bearing bone, the dentary, was braced at its back end. Realistic dinosaur costume The bracing came from a long upper prong or process of what was the main component of the rear of the jiw, the surangular. In avetheropods, this brace was missing, and philip Gingerich and Robert Bakker point out that a joint had formed at the mandible’s mid length, near its lower edge . Animatronic dinosaur costume In the front half of the jaw, lying inside the dentav, was a bone called the splenial; the angular helped to make up the back portion of the jaw. The front tip of the angular forrired a loosely articulated hinge joint with the central groove of the splenial.* such a “double-jointed” ja* would have been able to bow outward even further, increasing the size of things that could be bolted down.It is also possible, but less certain, that the joint had a vertical action as well that added impetus to its speed and force as it closed, greatly enhancing the jaw’s power. In fact, it is interesting that two groups of herbivorous avetheropods, the ostrich-mimics and the oviraptors, lost the doublejointed jaw because they no longer needed it. The first toothed birds did retain the hinge joint, but in many modern birds it is altered. The bones are bound trghtly together, but they are so thin that the jaws can still bow outward.