The name Tyrannosaurus Rex means ‘king of the tyrant lizards’ in Greek. It stood 4m tall and 12m long and weighed as much as 9 tons. It had very powerful legs and a muscular tail, which was necessary to balance its large, heavy head and permitted it to move quickly. Studies suggest the giant could run 10 to 25 mph. The T-rex's bite could utilize up to 13,000 pounds of pressure, which is equal to the force of a medium-sized elephant falling on top of you.When Dinosaurs Roamed the Earth:Episode 1