Tyrannosaurus rex

[ ti-ran-uh-sawr-uhs reks, tahy‐ ]
/ tɪˌræn əˈsɔr əs ˈreks, taɪ‐ /
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Also T. rex .

Origin of Tyrannosaurus rex

First recorded in 1905–10; New Latin Tyrannosaurus, the genus name; see tyrannosaur + Latin rex “king”; see rex
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is a Tyrannosaurus rex?

Tyrannosaurus rex was a giant, meat-eating dinosaur that walked on two legs and had a long tail and a big head with sharp teeth (and, yes, two little arms).

The name Tyrannosaurus rex comes from the Greek words tyranno (“tyrant”) and saurus (“lizard”) and the Latin word rex (“king”). So, Tyrannosaurus rex means something like “king of the tyrant lizards.” It is commonly called T. rex for short.

The name is fitting: Tyrannosaurus rex is one of the largest land predators that has ever lived. It was the largest of the tyrannosaurs, reaching a length of 47 feet (14.3 m) or more.

People often list the T. rex as their favorite dinosaur, and its popularity has grown through many pop culture depictions, such as its appearances in the Jurassic Park series of movies and books. However, to be scientifically precise about it, the T. rex lived during the Late Cretaceous period, about 90–65 million years ago, around the end of the age of dinosaurs.

Why is Tyrannosaurus rex important?

The first documented Tyrannosaurus rex fossils were discovered in Montana by paleontologist Barnum Brown, who would find more T. rex fossils over the next several years. Brown worked for the American Museum of Natural History, and the director of the museum, Henry Fairfield Osborn, is the one who gave the giant dinosaur its name in 1905.

Tyrannosaurus rex fossils have been found in the northwestern United States and parts of Canada. Based on fossil evidence, Tyrannosaurus rex grew to an average of 40 feet long and 12–15 feet tall, weighing an average of 14,000–18,000 pounds (6,400–8,200 kilograms). Tyrannosaurus rex was an especially muscular, scaly dinosaur that was bipedal (meaning it walked upright on two legs) with a large head and famously tiny forelimbs (arms). Tyrannosaurus rex was a carnivore and had an incredibly powerful jaw filled with long, razor-sharp teeth that it used to kill prey and tear flesh, which it would swallow in large pieces, bones and all, since it could not chew. Tyrannosaurus rex was a solitary animal that found food both as a scavenger, eating already dead animals, and as a fearsome predator that hunted and ate large herbivores such as Triceratops and Edmontosaurus. They sometimes even hunted each other. Due to its massive size, Tyrannosaurus rex is thought to have been a slow runner (about as fast as a human), and it is believed that it only lived to be 28 years old at most. Scientists are unsure of the exact mating habits of Tyrannosaurus rex but, as is presumed for all dinosaurs, it did lay eggs.

Compared to most other dinosaurs, Tyrannosaurus rex is among those that lived most recently. Because of this, paleontologists have been able to piece together nearly complete skeletons of the massive lizard king that have amazed museum visitors for years. Its popularity has contributed to the strong interest in dinosaurs and dinosaur fossils and the enduring popularity of dinosaurs in pop culture and the public imagination.

Did you know ... ?

The most complete skeleton of a Tyrannosaurus rex is currently on display in the Field Museum in Chicago, Illinois, and is nicknamed Sue, after its discoverer Sue Hendrickson. Sue (the dinosaur not the lady) found its home after a yearslong legal battle. The Field Museum, with help from Disney and McDonald’s among other donors, won an auction to buy the skeleton with a winning bid of $8.4 million dollars, which made Sue the most expensive fossil ever purchased at auction at the time.

What are real-life examples of Tyrannosaurus rex?

There have been many attempts to render what Tyrannosaurus rex may have really looked like based on fossil evidence and acquired knowledge of dinosaur anatomy. Though early movie depictions of T. rex made it look like a big green lizard standing upright, modern depictions are usually more accurate due to being done with the help of paleontologists.



What other words are related to Tyrannosaurus rex?

Quiz yourself!

Which of the following statements about Tyrannosaurus rex is NOT true? 

A. It lived in areas of what are now the United States and Canada.
B. It reached an average height of 12­–15 feet.
C. It was a plant eater.
D. It lived during the Late Cretaceous period around 90–65 million years ago.

How to use Tyrannosaurus rex in a sentence

Cultural definitions for Tyrannosaurus rex

Tyrannosaurus rex
[ (ti-ran-uh-sawr-uhs reks) ]

A large, carnivorous (see carnivore) dinosaur that walked on two legs. Its name is from the Greek words meaning “tyrant” and “lizard” and the Latin word for “king.”

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.