Tyrannosaurus rex
Tyrannosaurus rex was one of the largest land-living predators the world has ever known. The most complete skeletons, such as Sue and Scotty, represent animals around 12–13 metres long with hips standing a little over three and a half metres above the ground, and modern mass estimates usually fall between 6 and 9 tonnes.
Tyrannosaurus rex
Tyrannosaurus rex
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Quick facts
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Weight
6000–9000 kg
Length
11.5–13 m
Diet
Carnivore
Period
Cretaceous
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Tyrannosaurus rex next to Triceratops and a human, to the same scale.
Tyrannosaurus rex
Triceratops horridus
6000–9000 kg
11.5–13 m
Cretaceous
Bipedal
3.6–4 m
25 km/h
Carnivore
70 recorded fossil finds in United States, Canada, and Mexico. Most in North Dakota, Montana, and Wyoming. First described in 1905 by Osborn.
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Tyrannosaurus rex lived.
million years ago
Lived 68–66 million years ago
If the whole age of dinosaurs were a single day, Tyrannosaurus rex lived at 23:52.
Chapter • Meet the dinosaur
Tyrannosaurus rex was one of the largest land-living predators the world has ever known. The most complete skeletons, such as Sue and Scotty, represent animals around 12–13 metres long with hips standing a little over three and a half metres above the ground, and modern mass estimates usually fall between 6 and 9 tonnes. The body was carried horizontally, balanced over powerful hind limbs, with the heavy, muscular tail held out behind as a counterweight rather than dragging along the ground. The skull reached about 1.5 metres in length, lightened by large air-filled chambers and armed with teeth up to 30 centimetres long that were thick-rooted and built to crush bone. In contrast the arms were famously short, each with only two fingers, yet heavily muscled. Skin impressions from the neck, hips and tail show small, non-overlapping scales, while early relatives such as Yutyrannus preserve downy feathers, so most researchers now reconstruct a mainly scaly adult that may have retained a few filaments along the back.
Chapter • Where it lived
Tyrannosaurus rex lived during the final two million years of the Cretaceous, in the Maastrichtian stage about 68 to 66 million years ago. Its home was the low-lying coastal plain of western North America, along the shore of the vanished Western Interior Seaway. The landscape was a patchwork of broad river valleys, seasonally flooded floodplains, swamps and forests of conifers, magnolias and early broadleaf trees, with vast stands of ferns between them. The climate was warm and humid, with no permanent polar ice. The richest fossil sites are the Hell Creek Formation of Montana, South Dakota and North Dakota, the Lance Formation of Wyoming, and the Frenchman Formation of Saskatchewan in Canada. The same beds yield its prey, Triceratops and Edmontosaurus, and are capped by the boundary layer that marks the end-Cretaceous mass extinction.
Chapter • Wild behavior
Cathemeral
The bite force of an adult has been estimated at more than 35,000 newtons, the strongest measured for any land animal.
Casts of the braincase show enormous olfactory bulbs, suggesting a superb sense of smell.
Its eyes faced forward, giving overlapping fields of view and excellent depth perception.
Juveniles were long-legged and slender and could run considerably faster than the bulky adults.
Growth rings in the bones show a teenage growth spurt during which the animal put on roughly two kilograms a day.
An Edmontosaurus tail with a healed bite wound proves that T. rex attacked living prey and did not only scavenge.
The first skeleton was described in 1905 by Henry Fairfield Osborn, who named it 'tyrant lizard king'.
Despite its size it probably could not truly run; biomechanical models suggest fast walking at 18–27 km/h.
Chapter • Scientific place
Plazi TreatmentBank (original description: Osborn, Bulletin of the American Museum of Natural History)
Reviewed: 9/3/2026
Digitised treatment of Osborn's 1905 original description, which erected the genus and species and placed it within the theropod lineage leading to Tyrannosauridae.
Open sourcePLoS ONE
Reviewed: 9/3/2026
Documents the geographic and stratigraphic occurrence of Tyrannosaurus rex specimens through the Maastrichtian Hell Creek Formation of Montana, its principal fossil range.
Open sourceCanadian Journal of Earth Sciences
Reviewed: 9/3/2026
Reconstructs the coastal-plain, river-valley and floodplain palaeoenvironment in which Tyrannosaurus rex lived at the end of the Cretaceous.
Open sourcePeerJ
Reviewed: 9/3/2026
Analyses tooth marks on bone as direct physical evidence of the carnivorous feeding behaviour and prey processing of Tyrannosaurus rex.
Open sourceScience
Reviewed: 9/3/2026
Extinct taxon; conservation status NE
Open sourceSmithsonian National Museum of Natural History
Reviewed: 9/3/2026
Museum overview of Tyrannosaurus rex covering its anatomy, size, age and place in the Late Cretaceous ecosystem, used as the general description source.
Open sourceSmithsonian National Museum of Natural History
Reviewed: 9/3/2026
Museum overview of Tyrannosaurus rex covering its anatomy, size, age and place in the Late Cretaceous ecosystem, used as the general description source.
Open sourceSmithsonian National Museum of Natural History
Reviewed: 9/3/2026
Museum overview of Tyrannosaurus rex covering its anatomy, size, age and place in the Late Cretaceous ecosystem, used as the general description source.
Open sourceSmithsonian National Museum of Natural History
Reviewed: 9/3/2026
Museum overview of Tyrannosaurus rex covering its anatomy, size, age and place in the Late Cretaceous ecosystem, used as the general description source.
Open source
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