The tyrannosaurs were a group of large carnivorous (meat-eating) dinosaurs that roamed North America and Asia during the last part of the Cretaceous, 85 to 65 million years ago. The most famous tyrannosaur, is the fearsome, ferrocious Tyrannosaurus rex.
T.rex's skull alone measures 4 feet (1.2 m) long. The jaws of Tyrannosaurus rex were lined with dagger-shaped teeth, each of which were up to 6 inches (15 cm) long. The edges of T. rex's teeth were serrated like a steak knife, Its massive teeth and strong jaw muscles could easily penetrate the skin of an unarmored duck-bill dinosaur. While ripping off pieces of flesh with its jaws, Tyrannosaurus rex might have used its hind feet to hold down its victim.
Scientists are still debating two major theories of T-rex behavior. Was T-rex a predator or a scavenger? In other words, did it hunt and kill living animals like a tiger or did it eat animals which were already dead like a vulture?
Its awesome jaw, teeth, claws and legs suggest that it could easily overwhelm smaller dinosaurs and eat them. Its small eyes, pronounced sense of smell and slow running speed though are the characteristics of a scavenger. Most scientists suspect that T-rex probably did whatever it could to stay alive including both hunting and scavenging.
Another question which paleontologist ask is: Did T-rex lay eggs like other reptiles? Did they care for their young like their relatives, the birds? To date, no T-rex eggs have ever been found, nor any fossilized T-rex "families."
Of course, neither theory is any good without more study, more digging and more discussion!