Dinosaurs A to Z
Tyrannosauridae

Tyrannosaurus rex tih-RAN-uh-SOR-us REX

"Tyrant lizard king"

Tyrannosaurus silhouette
You 1.8 m (5.9 ft) tall
Tyrannosaurus 12 m (39 ft) long
as long as 7 people standing fingertip to fingertip
silhouette · T. Michael Keesey (CC-BY) via PhyloPic
Length
12 m (39 ft) — Up to 12.3 m and ~8 tonnes for the largest known individual (Scotty).
Period
Late Cretaceous (68–66 Mya)
Place
North America · Western United States · Alberta, Canada
Food
Carnivore — Large prey — hadrosaurs, ceratopsians, juvenile sauropods. Also a serious scavenger.
Clade
Tyrannosauridae Theropoda Coelurosauria Tyrannosauroidea Late-Cretaceous tyrants: T. rex, Tarbosaurus, Albertosaurus.

The last and largest of the tyrant kings.

Tyrannosaurus rex was one of the last and largest meat-eating dinosaurs, living in western North America right up until the asteroid strike that ended the Cretaceous. Adults stood about 4 m tall at the hip and walked on two powerful legs, carrying a head nearly 1.5 m long lined with banana-sized serrated teeth.

For a long time T. rex was drawn in a tail-dragging, upright “Godzilla” pose. That pose is wrong. The skeleton balances horizontally over the hips, tail held off the ground as a counterweight to the head — a posture that lets a 7-tonne animal turn quickly and bite with extraordinary force.

More about Tyrannosaurus

Discovery

Named by Henry Fairfield Osborn · 1905 · Hell Creek Formation, Montana, USA

The American Museum's fossil hunter Barnum Brown dug the first skeletons out of Montana; Osborn named the species Tyrannosaurus rex in 1905.

Greek and Latin for 'tyrant lizard king', Tyrannosaurus rex.

Portrait of Barnum Brown
Barnum Brown · 1873–1963 The American Museum of Natural History's star collector, who unearthed the first Tyrannosaurus skeletons and many more across the American West.
Did Tyrannosaurus have feathers?
Close relatives such as Yutyrannus preserve filament-like integumentThe body covering — skin, scales, feathers, or quills.. Skin patches from Tyrannosaurus itself show scales, so adults were probably mostly scaly, perhaps with sparse feathers. The debate is genuinely open.
Why such tiny arms?
The two-fingered arms were short but heavily muscled. Ideas run from gripping struggling prey to mating holds to simple reduction as the enormous head took over the killing, no consensus yet.

What we know

  • Over 50 known skeletons, more than any other large theropod.
  • Bite force ~35,000 N — strongest of any land animal ever measured.
  • Forward-facing eyes gave it strong binocular vision.
  • Tiny two-fingered arms, but heavily muscled.

What we guess

  • Probably had patches of feathers, especially when young. Adult body covering is debated — large body + warm climate suggests mostly scaly skin.
  • How fast it ran is contested. Modern estimates: a brisk walk (~20 km/h), not a Jeep-chasing sprint.
  • Whether it hunted alone or in groups — some bonebeds hint at packs, but the evidence is thin.