Its taxonomy is also controversial, as some scientists consider Tarbosaurus bataar from Asia to be a second Tyrannosaurus species while others maintain Tarbosaurus is a separate genus.
Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.
Relative to its large and powerful hind limbs, Tyrannosaurus fore limbs 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, 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.
(2011) found that the maximum weight of Sue, the largest complete Tyrannosaurus specimen, was between 9.5 and 18.5 metric tons (9.3–18.2 long tons; 10.5–20.4 short tons), though the authors stated that their upper and lower estimates were based on models with wide error bars and that they "consider [them] to be too skinny, too fat, or too disproportionate" and provided a mean estimate at 14 metric tons (15.4 short tons) for this specimen. (2009) tested dinosaur mass estimation procedures on elephants and concluded that those of dinosaurs are flawed and produce over-estimations; thus, the weight of Tyrannosaurus, as well as other dinosaurs, could have been much less.
Due to the relatively small number of recovered specimens and the large population of individuals present at any given time when Tyrannosaurus was alive, there could have easily been larger specimens than those currently known including "Sue", though discovery of these largest individuals may be forever untenable due to the incomplete nature of the fossil record.
Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods.
and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction.
Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail.
But in other respects Tyrannosaurus's skull was significantly different from those of large non-tyrannosauroid theropods.
It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.
The species Tyrannosaurus rex (rex meaning "king" in Latin), is one of the most well-represented of the large theropods.