Tyrannosaurus rex

*Albertosaurus lancensis*? (Gilmore, 1946), *Aublysodon lancensis*? (Gilmore, 1946)
*Deinodon lancensis*? (Gilmore, 1946)

### Museums and Zoos

National Museum of Natural History
National Zoological Park (skull only)

***Tyrannosaurus*** (meaning "tyrant lizard") is an extinct genus of large theropod dinosaur. The species ***Tyrannosaurus rex*** (*rex* meaning "king" in Latin), often called ***T. rex*** or colloquially ***T-Rex***, is one of the best represented members of the genus as well as all 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, 68-66 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.

Like other tyrannosaurids, *Tyrannosaurus* was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hind limbs, the forelimbs of *Tyrannosaurus* were short but unusually powerful for their size, and they had 2 clawed digits. The most complete specimen measures up to 12.3-12.4 meters (40.4-40.7 feet) in length and stands 3.66 meters (12 feet) tall, though *T. rex* could grow to lengths of around 13.2 meters (43.30 feet), up to 3.96 meters (13 feet) 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 strongest bite force among all terrestrial animals. By far the largest carnivore in its environment and the infamous "*king of the dinosaurs*", *Tyrannosaurus rex* was most likely an apex predator, preying upon hadrosaurs, juvenile armored 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 debates in paleontology. Most paleontologists today accept that *Tyrannosaurus* was both an active predator and a scavenger.

Specimens of *Tyrannosaurus rex* include some that are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits, physiology, and potential speed of *Tyrannosaurus rex* are a few subjects of debate. Its taxonomy is also controversial, as some scientists consider *Tarbosaurus bataar* from Asia to be a 2nd *Tyrannosaurus* species, while others maintain *Tarbosaurus* is a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with *Tyrannosaurus*.

In March 2022, new studies revealed there are three species of *Tyrannosaurus*, due to their different femurs and teeth incisors. The two other species are *Tyrannosaurus imperator* ("tyrant lizard emperor") and *Tyrannosaurus regina* ("tyrant lizard queen"). However, in late July of that year, this research has now been disproved, and only *Tyrannosaurus rex* currently exist.

As the archetypal theropod, *Tyrannosaurus* has been one of the best-known dinosaurs since the early 20th century and has been featured in film, advertising, postal stamps, and many other media.