Tyrannosaurus, meaning 'tyrant lizard', is a genus of theropod dinosaur. The famous species Tyrannosaurus rex ('rex' meaning 'king'), commonly abbreviated to T. rex, is a fixture in popular culture around the world. It lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils of T. rex are found in a variety of rock formations dating to the last three million years of the Cretaceous Period, approximately 68 to 65 million years ago; it was among the last dinosaurs to exist prior to the Cretaceous–Tertiary extinction event.
Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hind limbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two primary digits, along with a possible third vestigial digit. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring nearly 13 meters (43 feet) in length and up to 6.8 metric tons (7.5 short tons) in weight. By far the largest carnivore in its environment, T. rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger.
More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons.