A tyrannosaur (from the Greek τυράννος and σαῦρος, tyrannos and sauros, meaning “tyrant lizard” and “lizard”) is a species of predatory theropod dinosaur that lived during the Late Cretaceous period, around 85 to 65 million years ago. Tyrannosaurs were some of the largest land predators ever to have existed, with some individuals reaching lengths of over 12 metres (40 ft) and weighing up to 8 tonnes (17,600 lb).
Tyrannosaurs are thought to have been apex predators throughout much of their evolutionary history; however, they may have occasionally fallen prey to large carnivorous mammals such as Andrewsarchus or other members of their own family. Several genera are known, including Albertosaurus, Gorgosaurus, Nanotyrannus (sometimes considered a distinct genus), Panoplosaurus, Tarbosaurus and Tyrannosaurus itself; the latter is one of the best-known dinosaurs due to its prominence in popular culture. Fossils attributable to tyrannosaurids have been found on every continent except Antarctica.
Tyrannosaurid anatomy was characterized by numerous skeletal features that distinguished them from other theropods. They had shortened but deep skulls with many teeth set close together; these teeth were blade-like with serrated edges for cutting flesh. Their neck muscles were very powerful allowing them great mobility while hunting; their tails were thickened at the base providing additional support for their massive bodies. Like all dinosaurs they walked on two legs supported by muscular thighs; their forelimbs were much smaller than their hind limbs which ended in three-clawed toes armed with sharp talons used for grasping prey. The bones in their necks and tails were heavily reinforced by tendons running along each side making them extremely flexible allowing them to make quick turns while running at high speeds or help support their body weight when rearing up on two legs during feeding or fighting behaviours. Although most tyrannosaurs are thought to have been bipedal runners like modern day birds, some evidence suggests that at least some species may have also been capable of quadrupedal locomotion when necessary such as when moving through dense vegetation or climbing hillsides