The name Tyrannosaurus Rex means "Tyrant lizard king" in Greek, it is also known as T.rex. Tyrannosaurus Rex lived during the late Cretaceous Period, about 68-66 mya (million years ago). Tyrannosaurus Rex is the best known prehistoric animal that has ever lived. Tyrannosaurus Rex measures 12.25-13.65 meters (40.1-44.7 feet) long, stands 3.95-5.1 meters (12.9-16.7 feet) tall, and weighed about 8.4-14.1 tons (7620-12791 kg), meaning this dinosaur was one of the largest predatory dinosaurs ever to have existed. It was the largest terrestrial carnivore in North America (only succeeded in length by Saurophaganax, but not by weight). The largest T.rex skulls measure up to 1.45 meters (4.8 feet) in length, many other predators had similar skull lengths. Although Tyrannosaurus Rex wasn't the largest carnivorous dinosaur ever to walk the earth, it is still very facinating.