Achelousaurus is a type of ceratopsid dinosaur that lived in North America during the Late Cretaceous period, about 77 to 74.8 million years ago. The first fossils of Achelousaurus were found in Montana in the late 1980s by a team led by paleontologist Jack Horner. Achelousaurus was officially named and described in 1994 by Scott D. Sampson.
The name Achelousaurus comes from the Greek god Achelous, and it means “Achelous lizard.” The species Achelousaurus horneri is named after Jack Horner.
Achelousaurus was quite large, around 6 meters long and weighing about 3 tons. This dinosaur walked on all fours and had a large head with a unique beak. Its head also featured a bony frill at the back, with two long spikes curving outward. Unlike other related dinosaurs, adult Achelousaurus had round bumps over its eyes instead of horns. These bumps could have been used in fights or to attract mates.
The fossils of Achelousaurus have mainly been found in the Two Medicine Formation of Montana, an area that was once an island called Laramidia. As a plant-eater, Achelousaurus likely had a rapid metabolism, although not as fast as modern birds and mammals.
The discovery of Achelousaurus ties into discussions about how dinosaurs evolved. Some scientists believe it descended from a similar dinosaur called Einiosaurus and gave rise to another type called Pachyrhinosaurus. This evolution shows how dinosaurs changed over time.
Achelousaurus had some interesting features. Its skull was quite large, with a unique structure that helped it eat tough vegetation. The distinct bumps and frills on its skull were thought to have both practical and display functions, possibly used in fights or to show off to potential mates.
Overall, Achelousaurus is an important dinosaur for understanding the variety of ceratopsians and how evolutionary changes occurred in these fascinating creatures during the time of the dinosaurs.