The Achelousaurus was a herbivore Discovered in North America, Montana at the two Medicine Formation. Since it was found at the highest level its considered to be from the late Cretaceous Period. This was a very famous region for dinosaurs as the Daspletosaurus, Bambiraptor, Euoplocephalus, Maiasaura, and Einiosaurus.

The species was named after 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. In the Greek Myth it says that Hercules was fighting a Arhelousaurus and Hercules ripped off its horns.

The 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, two horns on the end of the neck frill.