Start with the question people ask most: how big was T. rex? T. rex was a big dinosaur that ate meat, and its name means "tyrant lizard king." Estimates for the length of the biggest T. rex run from about 40 to 46 feet, and it stood about 13 feet tall at the hips. A typical adult T. rex probably weighed between 5,000 and 7,000 kilograms. Henry Fairfield Osborn was the scientist who first named and described T. rex, and Barnum Brown found two early skeletons, in 1900 and 1902.

T. rex fossils have been found in western North America, in both the United States and Canada. As of August 2004, more than 30 T. rex skeletons had been found. T. rex was a top predator in a warm, humid, almost subtropical world with lush plants. Preserved skin patches from T. rex and its relatives show small pebbly scales, so as of November 2026 most of T. rex was probably not feathered. A partial covering is not ruled out. Yutyrannus, a feathered tyrannosaur relative, lived in a colder climate than T. rex, which may be why it had a feathery coat.

T. rex teeth were thick and blunt, not thin flat blades like those of most other meat-eating dinosaurs. It had about 60 teeth. As of May 2017 scientists put its bite at about 8,000 pounds of force, strong enough to crunch bones. T. rex ate large plant-eaters with thick bones, and some T. rex bones have bite marks from other tyrannosaurs. It also had a very good sense of smell. A 2006 study found a binocular range of 55 degrees, wider than a modern hawk's, so both eyes saw the same space ahead.

T. rex grew very fast when it was a teenager. It grew from about 1 ton to about 6 tons in roughly four years. It grew fastest between about age 14 and age 18. Scientists count growth rings in bones to tell how old a dinosaur was, much as people count the rings in a tree. T. rex stopped growing at about age 20 and spent about two-thirds of its life growing. It gained about 70 percent of its adult weight during that growth spurt, so T. rex lived fast and died young.

Sue is a famous T. rex skeleton that you can visit at the Field Museum in Chicago. Sue was found in South Dakota in 1990, and the skeleton is named after Sue Hendrickson, who found it. Digging Sue out of the ground took six people 17 days. Sue lived about 67 million years ago, and as of November 2026 the skeleton is one of the most complete T. rex skeletons ever found, about 90 percent complete. Sue's bones show that she was sick and hurt during her life. Scientists do not know if Sue was a girl or a boy.

Now look at a record holder, and then at how the story ended. As of March 2019, a T. rex nicknamed Scotty, found in Canada, is the largest T. rex known so far. Scotty is also the oldest T. rex known so far, and it seems to have lived to its early 30s, an unusually long life for a T. rex. A giant asteroid hit Earth about 66 million years ago, and T. rex and the other big dinosaurs died out. Yet birds are modern-day dinosaurs, and a pigeon is a distant relative of T. rex.

Words to know

• predator: a hunting animal
• humid: warm and damp
• binocular: using both eyes