Tyrannosaurus which means "tyrant," and sauros which means "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. The T. rex lived throughout what is now western North America, which then was an island continent named 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 Cretaceous Period, 67 to 66 million years ago. It was among the last non-avian dinosaurs to exist before the CretaceousâPaleogene extinction event.