Oklahoma designated Acrocanthosaurus atokensis as the official state dinosaur in 2006. This fearsome dinosaur had spines on its back and three six-inch claws on each forearm; it roamed the southern USA during the Middle Cretaceous period (125-112 million years ago).
Paleontologists discovered the first evidence of this dinosaur in the 1940s in Atoka County, Oklahoma (hence the atokensis in its name). They also found part of a skeleton in McCurtain County in the 1980s. Fossil evidence indicates that the Acrocanthosaurus atokensis is similar to the Tyrannosaurus rex, but it is millions of years older.