Tyrannosaurus was the largest of the "lizard-hipped" carnivorous dinosaurs known as theropods. It was a massive two legged predator> with a powerful tail, large head and tiny arms.

Its primary weapon was its mouth, with a 1.2 metre long jaw and a 1 metre gape. Curved serrated teeth, longer than a human hand, could be used to puncture an animal's organs, before Tyrannosaurus tore the flesh off. Tyrannosaurus could not chew, so had to swallow its food whole. It could probably gulp up to 70 kilograms in one go. One fossil shows the danger of this - a large carnivore had died swallowing, with two long bones stuck in its gullet.

Its tiny two-fingered arms seemed very small, but were believed to have been at least three times as strong as human arms. They were too short to reach its mouth, but were probably used as meat-hooks. There is clear evidence that tyrannosaurs fought one another from tooth-marks left in fossil remains.

The first reasonably complete Tyrannosaurus skeleton was discovered by palaeontologist Barnum Brown in Hell Creek, Montana, in the USA in 1902. Until this find only fragments had been unearthed. In all, over 20 individuals have been found, although, only three have complete skulls. Remains have been discovered from Alberta and Saskatchewan in Canada,to New Mexico, Montana, Texas, Utah, and Wyoming in the USA. Remains have also been found in Mongolia.