Tyrannosaurus (from tyrannos and sauros-Tyrant lizard) is a genus of theropod dinosaur. It lived throughout the area of present-day western North America, around 68 to 65.5 million years ago. Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Its front limbs were small, though unusually powerful for their size, bearing two clawed digits. It reached lengths of 12 to 15 meters and stood about 4 meters tall at the hip. The largest known skulls reached up to 1.5 meters in length. Tyrannosaurus teeth were robust and sharp like blades, curved backwards. New teeth grew continuously throughout its life, replacing the old ones.