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Tyrannosaurus rex
c. 68–66 million years ago· Fossil or site· Animals
Well establishedStrong fossil, genetic or geological evidence.
One of the largest meat-eating land animals ever, living in western North America in the last few million years before the asteroid.
See it on the Life map →What happened
Tyrannosaurus rex lived about 68–66 million years ago. Adults reached about 12 meters long and, by most estimates, 6–9 tonnes. Its bite was among the strongest of any land animal, able to crush bone. It had a keen sense of smell, forward-facing eyes for depth perception and famously small two-fingered arms. Growth rings in its bones show a rapid teenage growth spurt; few individuals lived past about 30.
Why it matters
The best-studied giant dinosaur, it is a reference point for how huge predators grew, fed and moved at the top of a food chain the asteroid then collapsed.
The evidence (fossils, genes, rocks)
Dozens of specimens, mostly from Montana's Hell Creek rocks; Barnum Brown found the first in 1902. 'Sue', about 90% complete, sold at auction for $8.4 million in 1997. Healed bite wounds on prey show it attacked live animals.
Still debated
Whether smaller skeletons called Nanotyrannus are young T. rex or a separate species is debated; a 2025 study argued separate. Skin patches show scales, so adults likely had few feathers.
Connections (3)
▸Dinosaurs include Tyrannosaurus rexWell established
The connection
T. rex belongs to the tyrannosaurs, a branch of the theropods, the meat-eating dinosaurs. For most of their history, from about 165 million years ago, tyrannosaurs were small and lightly built; only in the last 15–20 million years of the Cretaceous did they become giant top predators in Asia and North America.
When and how
Early tyrannosaur relatives such as Guanlong lived in China about 160 million years ago; T. rex lived in western North America about 68–66 million years ago.
The evidence
Shared skull, tooth and hip features place T. rex in the tyrannosaur family on dinosaur family trees, which agree across many independent analyses.
Debates and open questions
How tyrannosaurs grew so huge so late, and whether T. rex's direct ancestors came from Asia across a land bridge, are still studied.
▸Feathered dinosaurs of Liaoning include feathered relatives of Tyrannosaurus rexStrong evidence
The connection
Liaoning's ash beds yielded two feathered tyrannosaur relatives: Dilong, a small early form described in 2004, and Yutyrannus, about 9 meters long, described in 2012 with long filaments over its body. They show the tyrannosaur family had feathers, raising the question of whether T. rex did too.
When and how
Yixian Formation, Liaoning, northeast China, about 125 million years ago; described by Xu Xing and colleagues in 2004 and 2012.
How sure are we?
Filament impressions on the fossils themselves, and family trees placing Dilong and Yutyrannus among the tyrannosauroids, the wider group that includes T. rex.
Debates and open questions
Skin impressions from T. rex and its close relatives show scales (2017 study), so giant adults may have lost most feathers, perhaps to shed heat. Young ones may have been fuzzy.
▸Tyrannosaurus rex was among the last victims of K–Pg extinction: end of the non-bird dinosaursWell established
The connection
T. rex lived in the final few million years before the impact and was still a top predator in western North America when the asteroid hit. As a giant with large food needs, it depended on big plant-eaters such as Triceratops and Edmontosaurus, whose food supply collapsed in the darkness after impact.
When and how
Hell Creek Formation of Montana and the Dakotas, and similar rocks in Wyoming, Alberta and Saskatchewan, up to 66 million years ago.
The evidence
T. rex bones occur in the upper Hell Creek rocks, close below the boundary clay, and in no younger rocks anywhere.
Debates and open questions
Bones are scarce in the last few meters below the boundary, once read as a sign of decline before the impact; later finds have largely filled that 'three-meter gap'.