An exhibit which shows how tiny the front arms are compared with the skeleton as a whole. The skeleton behind it is an *Edmontonia*.   
Houston Museum of Natural History
Skeletons mounted together: Jurassic Museum of Asturias, Spain."Sue" in The Field Museum in Chicago is the most complete Tyrannosaurus skeleton
Brain cast of Charles, at the Portobello Fossil Museum
*Tyrannosaurus* and human size difference, showing many specimens
***Tyrannosaurus*** (name is from Greek: τύραννος "tyrannos" and σαῦρος "saurus", meaning "tyrant lizard") was a big predatory dinosaur from the Late Cretaceous, that lived in North America 68 to 65 million years ago.

*Tyrannosaurus* was a massive carnivore that walked on two legs and had a massive head, it had a long, heavy tail behind it so that it wouldn't fall over on its face. Compared to the big and strong legs, its arms were tiny, but strong for their size. They had two clawed fingers.

There is debate as to whether it was a hunter or a scavenger. Like most apex predators of today, like lions and hyenas, *Tyrannosaurus* might have been both. It had a very strong jaw, and its bite power could snap the bones of other dinosaurs. 

The most well known species of the genus tyrannosaurus is *Tyrannosaurus rex*. More than 30 skeletons have been found of it. Some of them are nearly complete skeletons, and soft tissue and proteins have been reported in at least one of these specimens. Research is done on its biology, life history and biological mechanics. The eating habits, physiology and potential speed of *Tyrannosaurus rex* are some topics of debate. Some scientists think *Tarbosaurus bataar* from Asia is a second species of *Tyrannosaurus*, but others think *Tarbosaurus* is a separate genus.

*Tyrannosaurus* became extinct in the Cretaceous–Tertiary extinction event, which wiped out 75% of all species on Earth.

Size
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The probable size of this dinosaur has changed many times. Packard and colleagues tested dinosaur mass calculations on elephants. They decided that dinosaur estimations are bad and produce results which were too high. Thus, the weight of *Tyrannosaurus* could be much less than usually estimated.

Although other theropods like *Giganotosaurus* and *Spinosaurus* could be similar to *Tyrannosaurus rex* in size, it was the largest known tyrannosaurid and one of the largest known land predators. It was up to 14 m (46 ft) in length, up to 4 metres (13 ft) tall at the head  and up to 10,659 kilograms (23,499 lb) in weight.

Skull
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The largest known *Tyrannosaurus rex* skulls measure up to 5 feet (1.5 m) in length. Big holes in the skull reduced weight and gave places for more muscles, *Tyrannosaurus*'s skull was very different from other large non-tyrannosaurid theropods. It was extremely wide at the back but had a narrow snout. This gave it good binocular vision. The skull bones were massive. Some bones were fused, preventing movement between them; but many had tiny air spaces inside them. This probably made the bones more flexible as well as lighter. Its bite was the strongest among dinosaurs.

The tip of the upper jaw was U-shaped (most non-tyrannosaurid theropods had V-shaped upper jaws), which increased the amount of flesh and bone a tyrannosaur could rip out with one bite, althougheverbeit it also increased the stresses on the front teeth.

First discovery
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The earliest *Tyrannosaurus* skeletons were found in 1902 by Barnum Brown. Henry Fairfield Osborn, president of the American Museum of Natural History, named the species *Tyrannosaurus rex* (meaning "tyrant lizard king") in 1905. The most complete skeleton was found in 1990 in South Dakota and named "Sue" after its finder, Susan Hendrickson. Several tyrannosaurids found later are also known by individual names. 

*Tyrannosaurus* has become well known. Many movies and television shows have featured it, such as Jurassic Park. Its skeletons are popular exhibits in many museums.

Jane
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"Jane" at the Burpee Museum in Rockford, Illinois
**Jane** is a fossil specimen of a small tyrannosaurid. It is either *Nanotyrannus* or a juvenile *Tyrannosaurus*. The skeleton was found in the Hell Creek Formation in southern Montana in 2001.

It took experts four years to make the partial skeleton ready for a museum. Jane went on display at Rockford, Illinois in the Burpee Museum of Natural History. Some paleontologists think Jane was a young tyrannosaurid, about 11 years old when she died. Jane is measured 6.5 metres (21.5 ft) long, about half as long as the largest known complete *T. rex* specimen, which is 13 m (42.6 ft) long. Experts think Jane weighed about 680 kg (1,500 lbs) when she was alive. Her large feet and long legs show she could perhaps run as fast as 20–30 miles per hour. Her lower jaw has 17 teeth. Her teeth are curved and serrated.

The scientists named her 'Jane' even though they do not know whether she was female. She was named after Jane Solem, a person who helped the Burpee Museum.

The Jane specimen has become part of an argument that scientists have. The scientists disagree whether *Nanotyrannus* is really a separate genus of tyrannosaurids. Jane's skull is almost exactly the same as the skull of the original *Nanotyrannus* specimen, which means they are the same species. The Burpee Museum held a conference in 2005. Paleontologists came to the conference and talked about whether these "pygmy tyrants" were adults from a small tyrannosaurid species or young *Tyrannosaurus rexes*. A few scientists thought they were adult small tyrannosaurids, but most of them decided they were probably young *T. rexes*.

Scotty
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Scotty exhibited in Japan
In August 1991, Robert Gebhardt was a high school principal. He joined Royal Saskatchewan Museum palaeontologists on a prospecting expedition. They went to the exposed bedrock along the Frenchman River Valley in southwest Saskatchewan, Canada. 
Gebhardt discovered the base of a worn tooth, and a vertebra from the tail. Both looked like they belonged to a *T. rex*. 

In June 1994, RSM palaeontologists began excavating the *T. rex*. The 66-million-year-old skeleton was the first *T. rex* skeleton found in Saskatchewan and one of only 12 known in the world at the time. **Scotty** is one of the largest and most complete skeletons with almost 70% of the skeleton found. A complete articulated cast of the skeleton was finally completed in 2012 and is now on display at its permanent home at the T.rex Discovery Centre in Eastend, Saskatchewan, Canada. 

Scotty's skull has a scar from the eye socket to the nostril. That was probably caused by another T. rex or large carnivore that gripped Scotty's skull in its jaws. The museum staff think this is the biggest T. rex specimen found. It weighed about 8,870 kg (8.87 tonnes). Scotty was perhaps in its early thirties at the time of death, and was 13 m (43 ft) long, including tail.

In popular culture
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Many people call it the "king of the dinosaurs". 

*Tyrannosaurus rex* appears in many works of fiction and literature. A *T. rex* is important in *A Sound of Thunder* by Ray Bradbury. A *T. rex* is a big part of the novel *Jurassic Park* by Michael Crichton, and Steven Spielberg's crew built a life-sized robot *T. rex* and a CGI *T. rex* for the movie version of *Jurassic Park*. Many other *T. rexes* have appeared in books, movies and animated works.

Related pages
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* Sue (dinosaur)
* Theropod
* Tyrannosauridae

Other websites
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* Tyrannosaurus on English Wikipedia