The Achelousaurus is an herbivorous kind of dinosaur that can grow up to be a maximum size of 6 meters long. The name "Achelousaurus" means "Achelous's lizard." It is known from the U.S. state of Montana in the Two Medicine Formation, and lived in North America during the Cretaceous period. It was named after Achelous since the three known skulls of Achelousaurus had rough bosses in the place where other ceratopsians had horns, making it look like its horns had been ripped off, and one of Achelous's horns were ripped off by Hercules, giving this dinosaur its name.