Tyrannosaurus rex

Tyrannosaurus rex fossils have been found only in western USA and Canada. However, other tyrannosaurids, like the closely related Tarbosaurus bataar, are known from eastern Asia.

Collecting dinosaur fossils from the Hell Creek badlands, Montana, USA. Source: Dept. of Library Services, © American Museum of Natural History

The first specimen of Tyrannosaurus rex was collected by Barnum Brown for the American Museum of Natural History in 1902. Additional specimens were not collected until the 1960s, when the Los Angeles County Museum of Natural History in California sent a collector to eastern Montana to search for more T. rex fossils. Parts of two skeletons of T. rex, plus a number of Triceratops specimens, were discovered. There has since been much effort devoted to finding and collecting specimens of T. rex, and there are now parts of more than twenty-one individuals known from western USA.

T. rex lived at the end of the Cretaceous period, and became extinct 65 million years ago along with the other dinosaurs of that period.

There are at least half a dozen other species of dinosaur belonging to the same family as T. rex, the family Tyrannosauridae, all from eastern Asia and North America. All tyrannosaurids lived during the Late Cretaceous period, and were alive for the final 20 million years of the time that the dinosaurs existed.

Tyrannosaurus rex. Artist: From an original painting by Kate Nolan. Source: Museum Victoria.

Tarbosaurus bataar. Artist: From an original painting by Kate Nolan. Source: Museum Victoria.

Besides the Tyrannosauridae, there were several other families of carnivorous dinosaurs. Of these other families the Allosauridae, and in particular the species Allosaurus fragilis, are best known. The largest A. fragilis specimen is almost as big as the large T. rex. The two can be simply distinguished from one another—A. fragilis had three fingers and a significantly larger forearm than T. rex, which had smaller forearms and only two fingers.