Tyrannosaurus rex

OLogy Series
extinct animal

Tyrannosaurus rex

OLogy Series
extinct animal

Given its 6-ton body, 4-foot jaw, and dagger-like teeth, no wonder paleontologists named this dinosaur "tyrant lizard king." T. rex was one of the largest carnivores (meat-eaters) ever. Like other theropod dinosaurs, T. rex walked on two legs and used its tail for balance.

Barnum Brown and the First T. rex Fossils
While hunting in Hell Creek, Montana in 1901, Dr. W.T. Hornaday found some large mysterious fossils. He showed photos of them to scientists at the American Museum of Natural History. Paleontologist Barnum Brown identified the bones as Triceratops remains. Excited, Brown led expeditions to Hell Creek, and in 1902 and 1908 he found the first two T. rex specimens. Although incomplete, these fossils revealed much about this dinosaur. Moving the fossils in the early 1900s was a headache. They had no power tools to dig out the remains, and often had to carry the bones by wagon over bumpy roads for many miles.

Follow the Tyranno Tracks
For nearly 80 years, the T. rex skeleton at the American Museum of Natural History stood upright, balanced on its legs and huge tail, like an enormous 3-legged stool. In 1993, scientists decided that this 3,500-pound fossil should be more "down to earth" in a stalking position. Because fossil footprints of dinosaurs almost never show their tails touching the ground, scientists reasoned that T. rex probably held its tail in the air for balance. Walking this way would have put much less pressure on its spine.

Most Tyrannosaurus rex fossils have been found in what part of the U.S.?

Oregon and Washington

New Mexico and Texas

Northwest Montana and South Dakota

Are you right?


Paleontologists have found most T. rex fossils in the Northwest, in states such as Montana and South Dakota.

Mark Norell

In our old exhibit, T. rex looked like Godzilla. Now it looks like a bird.

Scientific Name: Tyrannosaurus rex 
Pronunciation: tie-RAN-oh-SAW-rus rex
Meaning: "tyrant lizard king"
Locality Found: North America
Age: Late Cretaceous, 65 million years ago
Length: 12 to 18 meters (40 to 58 feet) long
Height: 6 meters (20 feet) tall
Weight: 6350 to 7260 kilograms (14,000 to 16,000 pounds; 7 to 8 tons)
Characteristics: T. rex had jagged teeth measuring 7.5 to 15 centimeters (3 to 6 inches) in length

Image credits: Rick Spears; Mark Norell: courtesy of Discovery Channel Online.