Tyrannosaurus is a genus of coelurosauriantheropoddinosaur. The speciesTyrannosaurus rex (rex meaning "king" in Latin), often called T. rex or colloquially T-Rex, is one of the most well-represented of the large theropods. Tyrannosaurus lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper CretaceousPeriod, 68 to 66 million years ago. It was the last known member of the tyrannosaurids, and among the last non-aviandinosaurs to exist before the Cretaceous–Paleogene extinction event. Like other tyrannosaurids, Tyrannosaurus was a bipedalcarnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hindlimbs, Tyrannosaurus forelimbs were short but unusually powerful for their size and had two clawed digits.