Tyrannosaurus rex

Tyrannosaurus rex lived near the end of the age of non-avian dinosaurs in western North America. Adults combined a broad, deep skull with thick, serrated teeth, a muscular neck, a barrel-shaped torso and a long counterbalancing tail. Its short arms were genuinely small but carried substantial muscle attachments and two clawed fingers. Several unusually complete skeletons—including SUE, the Wankel specimen and AMNH 5027—make adult anatomy well known. Even so, body mass, maximum speed, facial covering, juvenile taxonomy and the boundaries between proposed Tyrannosaurus species remain active research questions.

Its fossils occur between approximately 68 and 66 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was built to withstand large feeding loads: fused and braced bones formed a broad rear skull, while thick teeth could puncture and fracture bone. Growth was transformative rather than a simple enlargement. Juveniles had shallower skulls and proportionally longer, more slender legs; the torso and skull became much more robust as individuals approached adulthood. Skin impressions document small scales on limited parts of the body, but they do not preserve the entire covering.

• Broad, deep skull strengthened by fused and interlocking bones
• Thick, serrated teeth with rounded, bone-resistant cross sections
• Forward-facing eyes and a wide field of binocular overlap
• Short but muscular forelimbs ending in two functional fingers
• Large hip and thigh musculature powering the hind limbs
• Long, heavy tail balancing the head and torso
• Major skull and limb proportion changes during growth

Barnum Brown and Richard Swann Lull recovered the name-bearing skeleton in the Hell Creek beds of eastern Montana in 1902 for the American Museum of Natural History. Henry Fairfield Osborn named Tyrannosaurus rex in 1905; the specimen was then AMNH 973 and is now catalogued as CM 9380 at Carnegie Museum of Natural History. Brown found the more complete AMNH 5027 at Big Dry Creek in 1908. Its historic mount went on display in New York in 1915 and was later rebuilt in a horizontal, tail-raised posture as understanding of dinosaur balance changed.

Discovery credit: Barnum Brown, Richard Swann Lull.

Naming authors: Henry Fairfield Osborn.

T. rex occupied humid coastal lowlands east of the retreating Western Interior Seaway. The Hell Creek and equivalent formations preserve river channels, floodplains, ponds and forested habitats with seasonal disturbance. Triceratops, Edmontosaurus, ankylosaurs, pachycephalosaurs, turtles, crocodilians, mammals and many smaller vertebrates shared this landscape.

Direct evidence supports both predation and scavenging, so treating T. rex as exclusively one or the other creates a false choice. Its teeth, skull and neck could process large carcasses and damage bone, while healed bite marks and embedded tyrannosaur teeth show interactions with living animals. Bite force and running performance are reconstructed from models rather than observed directly. Evidence for coordinated pack hunting is inconclusive, and the function of the tiny arms remains unresolved.

• The holotype CM 9380 was discovered for the AMNH but transferred to Carnegie Museum in 1941.
• AMNH 5027 is about 45 percent original fossil; missing elements in the public mount are casts or reconstructions.
• SUE is about 90 percent complete by bone volume, and its original skull is displayed separately because it is too heavy and distorted for the standing mount.
• The Nation's T. rex was discovered by Kathy Wankel in 1988 and is on a 50-year loan to the Smithsonian.
• Juveniles were not miniature adults: their skulls and limbs changed markedly as they matured.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   The Paleobiology Database

   Open source
2. 02
   Tyrannosaurus and other Cretaceous carnivorous dinosaurs

   Henry Fairfield Osborn · Bulletin of the American Museum of Natural History · 1905

   Open source
3. 03
   Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull

   Christopher A. Brochu · Journal of Vertebrate Paleontology, Memoir 7 · 2003

   Open source
4. 04
   A computational analysis of limb and body dimensions in Tyrannosaurus rex with implications for locomotion, ontogeny, and growth

   John R. Hutchinson, Karl T. Bates, Julia Molnar and 2 coauthors · PLOS ONE · 2011

   Open source
5. 05
   Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics

   Karl T. Bates, Peter L. Falkingham · Biology Letters · 2012

   Open source
6. 06
   Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution

   Phil R. Bell, Nicolás E. Campione, W. Scott Persons IV and 4 coauthors · Biology Letters · 2017

   Open source
7. 07
   A high-resolution growth series of Tyrannosaurus rex obtained from multiple lines of evidence

   Thomas D. Carr · PeerJ · 2020

   Open source
8. 08
   Tyrannosaurus rex fossil: specimen AMNH 5027

   American Museum of Natural History

   Open source
9. 09
   Visiting SUE the T. rex: what to know before you go

   Field Museum

   Open source
10. 10
    The Nation's T. rex

    Smithsonian National Museum of Natural History

    Open source
11. 11
    Dinosaurtiden

    Museum of Evolution

    Open source