Manus and Pes. T. rex claws are part of its very important tool kit. The outside, or "nail," of the claw has not been preserved for T. rex, but we know from other animals (including some dinosaurs) that the actual sheath of the claw extended way beyond the bone. This means that the four-inch bony part of the thumb claw would be covered with a six-inch sheath. Hand, or manus claws, are narrow, strongly curved, and designed as meat hooks to grasp prey. Foot, or pes claws, are broad, weakly curved, and were used for traction, and possibly defense.

Cats are the only living animals that have retractable claws. In extinct animals, we can tell from the fossils whether the claws retracted - most cats' did and some, like the living cheetah, didn't. In dinosaurs, only one group had retractable claws, and theirs was the single "killer" claw of the foot. Can you guess which group of creatures this was?

The teeth in your mouth have different shapes and functions - sharp ones cut food; flat ones mash it up. T. rex had only one basic shape of tooth: pointy, serrated bananas (although they vary slightly, from rounder to D-shaped to skinnier, and come in different sizes). T. rex had no mashing teeth, which means no chewing! Imagine what that meant for T. rex's eating habits: bite, shear, swallow.

The lower, or dentary, teeth are rounder in cross-section than the upper, or maxillary teeth. All T. rex teeth have two serrated edges for cutting. Most have one in front and one in the back, but the position of the serrations depends on each tooth's position in the mouth. The serrations follow the shape of the jaw, like a cookie cutter - so T. rex could bite chunks that would fit in its mouth. At the back of the mouth, serrations are at the front and back; by the time you get to the front of the jaw, the serrations are both on the back of the tooth.

Scientists usually find T. rex teeth in two conditions: shed and rooted. A whole tooth, with its root still attached, looks rather like an entire banana. The presence of rooted teeth at a dig site is excellent evidence that the skull is nearby; the creature died with those teeth in its mouth, and they didn't fall out until they rotted out. Shed teeth are basically broken off into the shape of half a banana (top or bottom). Shedding would occur during eating or fighting, and we find shed teeth at excavations of animals that made up T. rex's diet.

In T. rex, tooth replacement happened much differently than in the human mouth, which allows for only one set of baby teeth and one set of adult teeth. T. rex kept growing new teeth throughout their lives.