Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Ornithischia
Suborder: Marginocephalia
Superfamily: Ceratopsia
Family: Ceratopsidae
Subfamily: Centrosaurinae
Genus: Achelousaurus

Species: A. Horneri

A. horneri was a medium-sized ceratopsid dinosaur that lived during the late Cretaceous (85 to 70 million years ago). Like all other members of its family, it had a bony neck frill, a large, parrot-like beak, and various herbivorous adaptations. Cranial modifications unique to A. horneri include two large horns at the top of the serrated frill, and raised projections of rough bone (known as bosses) above the eyes and over the snout. The true purpose of the facial elements remains debated, although it is speculated that it was used for intraspecies sexual selection and competition.

Type Species: Achelousaurus horneri

Sampson, SD. (1995). Two new horned dinosaurs from the Upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae). Journal of Vertebrate Paleontology Vol. 15, No. 4, pp. 743-760.

Locality:

Two Medicine Formation, Montana, USA.

Scientific Resources:

Ryan, MJ. (2007). A New Basal Centrosaurine Ceratopsid from the Oldman Formation, Southeastern Alberta. Journal of Paleontology, Vol. 81, Issue 2, pp. 376-396.

Tanke, D; and Carpenter, K. (2001). Mesozoic Vertebrate Life. Indiana University Press.

Barrick, RE; Showers, WJ; and Fischer, AG. (1996). Comparison of Thermoregulation of Four Ornithischian Dinosaurs and a Varanid Lizard from the Cretaceous Two Medicine Formation: Evidence from Oxygen Isotopes. Palaios, Vol. 11, No. 4, pp. 295-305.