Since it was found at the highest level it is considered to be from the late Cretaceous Period. This was a very famous region for dinosaurs such as Daspletosaurus, Bambiraptor, Euoplocephalus, Maiasaura, and Einiosaurus. The species was named by Scott Sampson after he discovered three skull fossils of the dinosaur. This was in 1995. It is part of the Ceratopsidae family. It was named in reference to a river deity from ancient Greek myth called Achelous who lost his horn in a battle against Hercules.The skull of Achelousaurus has a low,flat boss on its snout that looks like the animal has had its horn broken off.
Achelousaurus was about 20 feet long, and could weigh up to 6 tons. One skull found was 5 feet long. It had a beak for a mouth that somewhat resembled a parrot, a raised bony area on the snout and two behind the eyes,as well as two horns on the end of the neck frill.