Barnum Brown Discovered T. rex

The first Tyrannosaurus rex fossil was discovered by the famous fossil hunter Barnum Brown in 1902. T. rex was named in 1905 by Henry Fairfield Osborn. That same years, Osborn also named another huge Cretaceous theropod, calling it Dynamosaurus imperiosus (meaning "powerful, mighty lizard"). Osborn later made Dynamosaurus a synonym of Tyrannosaurus, realizing that they were the same.

Henry F. Osborn Named T. rex

In 2000, Jack and Celeste Horner, Bob Harmon, Larry Boychuk, and Greg Wilson found 5 T. rex fossils on Federal property (near the Fort Peck Reservoir) in Montana, USA. This was the first time more than one T. rex was found in one spot.

Tinker (or Kid rex), a juvenile T. rex, was found in the Hell Creek Formation of western South Dakota, USA. Tinker was about 5 to 6 years old at the time of its death. This tiny T. rex was about 2/3 the size of an adult but only about 1/4 of an adult's weight. Tinker's skeleton is about 70% complete.

None of these fossils are complete, so no one knows exactly how many bones a T. rex had. It probably had about 200 bones, roughly the same as us.

Sue is a huge, almost complete T. rex fossil that was found by Susan Hendrickson near Faith, South Dakota, in August 1990. After much controversy about its ownership (and other legal matter), Sue (the T. rex) was auctioned at Sotheby's in 1997 for $7.6 million dollars to the Field Museum in Chicago. Sue is on view at the Field museum, Chicago, Illinois, USA.

• T. rex (type species: Osborn, 1905, found in Alberta, Saskatchewan, Colorado, Montana, New Mexico, N. Dakota, S. Dakota, and Wyoming) - 10-14 m
• T. bataar (Maleev, 1955, found in China, Mongolia) - 9-12 m
• T. efremovi (Maleev, 1955 - originally Tarbosaurus, found in Mongolia) - 7-8 m
• T. lancesis (Gilmore, 1946 - originally Gorgosaurus, found in Montana, USA) - 5 m
• T. movojilovi (Maleev, 1955 - originally Gorgosaurus, found in Mongolia) - 6 m