In Hand Museum - Tyrannosaurus rex

Tyrannosaurus rex is probably the most famous of all dinosaurs. For almost a century it has fascinated dinosaur lovers of all ages. Everything about this animal was huge: its teeth; its head; its clawed feet; and, more than likely, its appetite. T. rex was one of the largest terrestrial, meat-eating animals that ever lived; it reached lengths of 14 meters (45 feet) and weighed over 5 tons, or about the weight of a modern African elephant. T. rex stood on two pillar-like legs with its 6 meter tail extended back to counter-balance a massive 1.4-meter long head. Scientists have yet to figure out how T. rex used its tiny, two-clawed arms.

This "tyrant lizard king" hunted hadrosaurs and ceratopsian herbivores 65-67 million years ago during the Late Cretaceous. Its fossilized remains have been found in western North America.

Taxonomy

The taxonomic relationships of dinosaurs are a complicated arrangement full of long Greek and Latin words. This complex system helps us understand which dinosaurs are related to one another as well as the characteristics they have in common. The systematics of a specimen tell the story of its lineage and evolutionary relationships.Tyrannosaurus rex is a theropod, a group of specialized predators which can be distinguished from other dinosaurs by over 20 skeletal features unique to this group. These characteristics include clawed hands, hollow bones and a bipedal stance for walking and running among them. Most theropod dinosaurs fall into three subgroups: the more primitive ceratosaurs; the large carnosaurs; and the smaller, bird like coelurosaurs. To go one more step, we group carnosaurs into two families: Allosauridae and Tyrannosauridae. T. rex, Albertosaurus, Nanotyrannus, Tarbosaurus and Daspletosaurus are all tyrannosaurs.

Anatomy
When you study the skull of Tyrannosaurus rex, several things stand out. The teeth are always noticed. They were large and dangerous. They grew up to 20 cm in length (7"). The upper and lower teeth did not touch when the mouth was closed. Rather, they passed near each other like blades of scissors, cutting sections of flesh out of the prey. Because of the configuration of the upper and lower teeth, Tyrannosaurus did not chew it's food, but had to swallow chunks of meat whole. All its teeth had serrations on both front and back edges. It is thought that these serrations acted to increase the cutting ability of the tooth during eating. Teeth were constantly forming, erupting and falling out during the lifetime of the animal. As one tooth was being used, another was forming to take its place, as in modern sharks.

When you look at the skull from the top, you'll notice that the snout is narrow compared to the back of the head allowing, the eyes to look more forward. T. rex may have had some degree of stereoscopic vision, like humans. This would have helped it find and track its prey. Most other theropods had eyes on the sides of their heads like birds.

Unlike the lightly built, open structured Allosaurus skull that combines strength and light weight, T. rex's skull is heavily boned and built to withstand powerful impacts and stresses. This characteristic is also carried over into other areas of the skeleton such as the neck and spine. Its feeding habits must have called for great strength. A close look at the snout reveals a rough, pitted area above the teeth. The holes allowed blood vessels and nerves to reach the skin of the snout area and the rough parts could have been for muscle attachment.

The ball joint at the back of the skull was a very flexible connection to the neck that allowed the head to twist with struggling prey without loosening its grip. Deep inside the skull, T. rex's brain was well protected. While it was larger than a human brain, it was small for such a large animal and was mostly dedicated to sight and smell rather than thinking.

[ Dinosauria -> Saurischia -> Theropoda -> Tetanurae -> Coelurosauria -> Tyrannosauridae ]

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