The jaws of a Tyrannosaurus rex are imposing in size. At lengths of 13 meters or 43 feet, the Tyrannosaurus rex also had huge jaws capable of biting into the bones of its prey. The bones in the skull are pretty static since they are fused together. The Tyrannosaurus rex has serrated teeth but instead of being pointy and knife-like, they are in fact oval and enormous. Most carnivorous dinosaurs have teeth that are flattened on either side and comparable to daggers. The Tyrannosaurus rex however, has serrated teeth but they are comparable to bananas and very dangerous due to the power of the jaws. Because the teeth of this huge carnivore were used so often, it was advantageous for the dinosaur to have teeth that never stopped growing. Although the Tyrannosaurus rex had a larger brain than many other carnivores at that time it was probably not the smartest creature roaming the Earth.

The tiny arms of the Tyrannosaurus rex were most likely used to assist the dinosaur when getting up from the ground. Another purpose would have been to assist in reproduction. The fully mature Tyrannosaurus rex were probably much slower than the younger Tyrannosaurus rex. To make the dinosaur more structurally reasonable, most of the bones were hollow allowing for good support without the extra weight.