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Tyrannosaurus rex

probably the most easily recognized and most famous of all dinosaurs

The name Tyrannosaurus rex means "king tyrant lizard," a name it received because of its very sharp teeth and rather fearsome appearance. It lived during the late Cretaceous Period, about 85 to 65 million years ago.

Tyrannosaurus rex


The largest flesh-eating animal that has ever walked the earth, Tyrannosaurus rex was up to 40 feet long, stood about 20 feet high and weighed about 7 tons.

Its small "arms" ended in clutching "hands" and curved claws longer than those of today's biggest bear. The claws on the three-toed hind feet were about 8 inches long. The head was almost 5 feet long and its jaws were filled with 50 to 60 one-inch-thick, 6-inch-long teeth, pointed like daggers and saw-toothed like the cutting edge of a steak knife.

Fossilized skin specimens have been found indicating that Tyrannosaurus rex had rough, scaly skin similar to that of an alligator.

Placement of the eye sockets in the skull, combined with large visual lobes in the brain, suggests that Tyrannosaurus rex had depth perception. It also had a very large area in the brain for processing odors.

Distribution and Habitat

Based on where fossils have been found, Tyrannosaurus rex lived in humid, semi-tropical environments, in open forests with nearby rivers, and in coastal forested swamps. Fossils have been in western North America (Montana, Texas, Utah, and Wyoming), Canada (Alberta and Saskatchewan), and Mongolia.


Tyrannosaurus rex most definitely ate meat, as indicated by its teeth and by fossilized dung. However, there is considerable debate amongst paleontologists as to whether it was a hunter or scavenger.

Fossil Record

The first Tyrannosaurus rex fossils were found by noted fossil hunter Barnum Brown in Hell Creek, Montana, in 1902. The species was named by Henry Fairfield Osborn in 1905.

Since the first fossils were found, a total of about 30 incomplete skeletons have been unearthed, including one juvenile. One footprint has been found in New Mexico, and there are also a few fossilized dung specimens.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Archosauria
order Saurischia
suborder Theropoda
family Tyrannosauroidea
genus and species Tyrannosaurus rex

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The Robinson Library >> Paleontology

This page was last updated on 09/15/2018.