<Li> Stygivenator molnari (Paul, 1988) </Li> <Li> Dinotyrannus megagracilis Olshevsky & Ford, 1995 </Li> <P> Tyrannosaurus is a genus of coelurosaurian theropod dinosaur . The species Tyrannosaurus rex (rex meaning "king" in Latin), often colloquialy called simply T. rex or 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 Cretaceous Period, 68 to 66 million years ago . It was the last known member of the tyrannosaurids, and among the last non-avian dinosaurs to exist before the Cretaceous--Paleogene extinction event . </P> <P> Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore 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 . The most complete specimen measures up to 12.3 m (40 ft) in length, up to 3.66 meters (12 ft) tall at the hips, and according to most modern estimates 8.4 metric tons (9.3 short tons) to 14 metric tons (15.4 short tons) in weight . Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it is still among the largest known land predators and is estimated to have exerted the largest bite force among all terrestrial animals . By far the largest carnivore in its environment, Tyrannosaurus rex was most likely an apex predator, preying upon hadrosaurs, armoured herbivores like ceratopsians and ankylosaurs, and possibly sauropods . Some experts have suggested the dinosaur was primarily a scavenger . The question of whether Tyrannosaurus was an apex predator or a pure scavenger was among the longest ongoing debates in paleontology . </P>

When did the tyrannosaurus rules as apex predator