Tyrannosaurus Rex was a bipedal saurischian (lizard hipped) theropod and possibly the largest carnivore to have ever walked the earth. Its large head was crammed full of sharp serrated teeth that were designed for crunching bone. There is a great debate on whether T-Rex was a hunter or a scavenger. Some argue that its large size was an impediment when hunting and that if it fell over whilst running it would probably have caused itself sever, if not life threatening, injuries.

Tyrannosaurus Rex had two very short, almost comical, front arms, each with two fingers. The two large feet each had three main toes, with claws, and a minor vestigial fourth toe with a tiny claw on it. The tail was long and stiff to counterbalance the large head and body. The body was muscular and well built but the skeleton consisted of hollow bones that made it strong and light, much like a modern bird's.

The only predator capable of threatening an adult Tyrannosaurs Rex would have been another Tyrannosaurus. Old, weak or young specimens, however, would have been at risk from other smaller carnivores too.

Tyrannosaurus Rex would have preyed upon duck billed dinosaurs and Hadrosaurs that would have been common in the forests of the late Cretaceous. Tyrannosaurus would have presumably ambushed its prey, sprinting over a short distance after its intended victim.

The first fossils of Tyrannosaurus Rex were found in western USA in 1902. No complete skeleton has been found and early attempts at reconstruction inaccurately portrayed T-Rex standing at an angle of 45 degrees. Recent, more complete Tyrannosaurus, finds have allowed palaeontologists to identify the correct stance, which is more like a bird's.