# Tyrannosaurus - Source: Wikijunior (en.wikibooks.org), CC BY-SA 4.0, Wikijunior contributors - Reading level: Grades 3 and 4 - Subjects: Dinosaurs, Animals, Nature - Topics: tyrannosaurus, dinosaurs, template, found, long, time - Length: 900 words, about 6 min - Published: 2024-04-03 - Original: - Page: - Open in Sprouts: ![](https://sprout.rootsofreason.org/media/wikijunior-wikijunior-dinosaurs-tyrannosaurus-wikibooks-open-books-for-an-open-wo-ee6ed58899.jpg) *T. rex* with feathers in Stockholm. *Tyrannosaurus*, "tyrant lizard", or "Tyrannosaurus rex (Tyrant lizard king)", *T. rex* for short, was a dinosaur that lived in North America about 68 to 66 million years ago, during the end of the Cretaceous period. *T. rex* is one of the largest carnivorous (meat-eating) dinosaurs ever discovered. It is also quite likely the best-known dinosaur of all. ### What was their body shape? ![](https://sprout.rootsofreason.org/media/wikijunior-wikijunior-dinosaurs-tyrannosaurus-wikibooks-open-books-for-an-open-wo-a2397eaea4.jpg) *T. rex* skeleton from the Smithsonian Museum of Natural History *Tyrannosaurus rex* was up to 12.4 meters (40.7 feet) long and 3.66 meters (12 feet) tall, and weighed 10 tons (11.03 US tons) – bigger than a bus, and as heavy as two African bush elephant. That's as an adult. T. rex when first hatched was probably about the size of a turkey. T. rex had a forward tilt, deep jaws, huge teeth, a long tail, and tiny arms (also known as forelimbs). *T. rex'*s jaw alone was about 1.3 meters long and had fifty to sixty bone-crunching teeth that were up to 10 centimeters or 6 inches long. Its arms were very stubby, no longer than an average person's. They were still very strong, able to lift up to two hundred kilograms, but were not long enough to touch each other! *T. rex* stood on two powerful hind legs, each ending with a three-toed foot, resembling a bird's foot, only much larger. ### What did they eat? ![](https://sprout.rootsofreason.org/media/wikijunior-wikijunior-dinosaurs-tyrannosaurus-wikibooks-open-books-for-an-open-wo-2e95316340.jpg) *T. rex* skull from the *Palais de la Découverte* in Paris *T. rex* was a very big meat-eating dinosaur, also called a carnivore. It would have been at the top of the food chain. It is known to have fed on other large dinosaurs, such as *Edmontosaurus*, *Anatosaurus*, and *[Triceratops](https://sprout.rootsofreason.org/r/wikijunior/wikijunior-dinosaurs-triceratops-wikibooks-open-books-for-an-open-worl)*, and probably could have swallowed smaller dinosaurs in a single bite. One scientist believes that *T. rex* was a scavenger (an animal that eats already dead animals). He argues that it might not have been fast enough to catch prey. Other scientists believe that *T. rex* probably scavenged and hunted, like most living meat-eaters (such as tigers and lions). *T. rex* bite marks found on the bones of *Edmontosaurus* and *Triceratops* that have healed show that *Tyrannosaurus* did hunt at least some of the time – and also that its prey was sometimes lucky enough to escape. One thing that *T. rex* did not eat was people. People didn't appear on Earth until over 60 million years later, much too late for anyone ever to be afraid of being hunted down by a *T. rex*. ### When did they live? *Tyrannosaurus* lived about 68 to 66 million years ago, in the late Cretaceous Period. *T. rex* was among the last of the big dinosaurs. Like all non-bird dinosaurs, *T. rex* lived in the Mesozoic era. ### What was their habitat? *Tyrannosaurus* is believed to have lived in forests, near rivers, and in areas that were open and full of prey. Mild seasons would have been most favorable to it. *Tyrannosaurus* fossils have been found in western North America and possibly Asia. ![](https://sprout.rootsofreason.org/media/wikijunior-wikijunior-dinosaurs-tyrannosaurus-wikibooks-open-books-for-an-open-wo-03c39c1ce4.jpg) *T. rex* footprint at a museum ### How were they discovered? The famous fossil hunter Barnum Brown found the first *Tyrannosaurus* fossil in 1905. *Tyrannosaurus* was not the dinosaur's name until 1905, when it was given that name by Henry Fairfield Osborn. About 3,000 *Tyrannosaurus* fossils have been found, from pieces of teeth to nearly complete skeletons. Only one possible *Tyrannosaurus* footprint has been found. ### What do we need to learn? - The color of their skin. One thing we cannot tell from fossils is color! - Whether *T. rex* was feathered, scaly, or both. Some of its cousins had feathers like birds, while others had scales, so it likely had both. - Whether *T. rex* was just a scavenger or a scavenger and a hunter. There are very few hunting animals that will not scavenge, and very few scavengers which never hunt. - If *T. rex* had the ability to run. - Was it really the largest predator? In 1995, parts of a predator that seems even larger than *T. rex* were found in Argentina! It was called *Giganotosaurus* and was about 45 ft long (about a meter \[yard\] longer than *T. rex*). Since then, parts of even larger carnivorous dinosaurs, such as *Spinosaurus* and *Carcharodontosaurus*, have been found. 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Rendering was triggered because: unknown ## Picture credits - Marcin Polak from Warszawa / Warsaw, Polska / Poland, CC BY 2.0 () - Quadell, CC BY-SA 3.0 () - Copyright © 2005 David Monniaux, CC BY-SA 3.0 () - CC BY 2.0 ()