Facts about Sue the Tyrannosaurus rex, as provided by the Field Museum in Chicago:
The animal weighed about 7 tons when alive, with a skull 5.2 feet long. Yet its brain cavity was only about large enough to hold a quart of milk.
Six fossil hunters spent 17 days extracting the dinosaur from the ground. But 10 preparators needed two years to clean and repair the bones for exhibit.
A T. rex skeleton is made up of more than 250 bones. Only a few are missing from Sue's skeleton: a foot, one arm, a few ribs and vertebrae.
Only two complete T. rex forelimbs have been discovered anywhere in the world. Sue's is one of the two.
Sue's legs are enormous, but her arms are the size of a human's. Compared with her vast bulk, they are tiny. The forelimbs are so small her hands could not even reach her mouth. "No one knows how T. rex used those tiny forelimbs," says an expert from the Field Museum.
A Tyrannosaurus rex would shed and regrow its razor-sharp teeth throughout its life.
Dinosaurs evolved from a group of crocodile-like reptiles called thecodonts.