Tyrannosaurus rex, often called T. rex, was one of the largest and most fearsome carnivorous dinosaurs that ever lived. It roamed the Earth during the Late Cretaceous period, about 68 to 66 million years ago. T. rex measured up to 12 meters (40 feet) in length, stood around 4 meters (13 feet) tall at the hips, and weighed as much as 9 metric tons. It had an enormous skull filled with large, serrated teeth that could crush bone, and its bite force was one of the strongest of any known terrestrial animal. Despite its small, two-fingered arms, T. rex was a highly effective predator, likely preying on large herbivores such as Triceratops and Edmontosaurus. Fossils of T. rex have been found in North America, particularly in the United States and Canada, and it remains one of the most iconic dinosaurs in history.