Skull of holotype specimen MOR 485 (with reconstructed parts in blue-gray), at the Museum of the Rockies, Montana
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Dinosauria
Clade:
†Ornithischia
Clade:
†Ceratopsia
Family:
†Ceratopsidae
Subfamily:
†Centrosaurinae
Tribe:
†Pachyrhinosaurini
Clade:
†Pachyrostra
Genus:
†Achelousaurus Sampson, 1994
Species:
†A. horneri
Binomial name
†Achelousaurus horneri
Sampson, 1994
Achelousaurus (/əˌkiːloʊˈsɔːrəs,ˌækɪˌloʊəˈsɔːrəs/[1]) is a genus of centrosaurine ceratopsid dinosaur that lived during the Late Cretaceous Period of what is now North America, about 74.2 million years ago. The first fossils of Achelousaurus were collected in Montana in 1987, by a team led by Jack Horner, with more finds made in 1989. In 1994, Achelousaurus horneri was described and named by Scott D. Sampson; the generic name means "Achelous lizard", in reference to the Greek deity Achelous, and the specific name refers to Horner. The genus is known from a few specimens consisting mainly of skull material from individuals, ranging from juveniles to adults.
A large centrosaurine, Achelousaurus supposedly was about 6 m (20 ft) long, with a weight of about 3 t (3.3 short tons). As a ceratopsian, it walked on all fours, had a short tail and a large head with a hooked beak. It had a bony neck-frill at the rear of the skull, which sported a pair of long spikes, which curved towards the outside. Adult Achelousaurus had rough bosses (roundish protuberances) above the eyes and on the snout where other centrosaurines often had horns in the same positions. These bosses were covered by a thick layer of keratin, but their exact shape in life is uncertain. Some researchers hypothesize that the bosses were used in fights, with the animals butting each other's heads, as well as for display.
Within the Ceratopsia, Achelousaurus lies within the clade Pachyrostra (or "thick-snouts"). It has been suggested that it was the direct descendant of the similar genus Einiosaurus (which had spikes but no bosses) and the direct ancestor of Pachyrhinosaurus (which had larger bosses). The first two genera would be transitional forms, evolving through anagenesis from Styracosaurus. There has been debate about this theory, with later discoveries showing that Achelousaurus is closely related to Pachyrhinosaurus in the group Pachyrhinosaurini. Achelousaurus is known from the Two Medicine Formation and lived in the island continent of Laramidia. As a ceratopsian, Achelousaurus would have been a herbivore and it appears to have had a high metabolic rate, though lower than that of modern mammals and birds.
^Creisler, B. (1999). "Beipiaosaurus and Caudipteryx pronunciation". Dinosaur Mailing List (Mailing list). Retrieved September 26, 2017. This one has to be pronounced ak-e-LOH-uh-SAWR-us, NOT a-KEE-lo-SAWR-us, as I recall hearing. The name derives from Greek Akheloos (the two o's being pronounced separately), which Latin rules turn into Achelous (divided as a-che-lo-us, short e, long o and short u), again pronounced in four syllables with the accent on the next-to-last, that is the one with the long o. All sources I have checked indicate that ak-e-LOH-us is the accepted English pronunciation of the Latin name. Since the scientific name Achelousaurus was formed by arbitrarily combining Achelous and saurus instead of using the stem-form Achelo-, the "u" needs to pronounced.
fossils of Achelousaurus were collected in Montana in 1987, by a team led by Jack Horner, with more finds made in 1989. In 1994, Achelousaurus horneri was...
albertensis, but in a clade including Pachyrhinosaurus, Einiosaurus and Achelousaurus, and therefore McDonald and Horner gave the species the new genus name...
Styracosaurus, Stellasaurus, Einiosaurus, Achelousaurus, and Pachyrhinosaurus. Pachyrhinosaurus and Achelousaurus form the clade of pachyrhinosaurins called...
intraspecific combat. The massive bosses on the skulls of Pachyrhinosaurus and Achelousaurus resemble those formed by the base of the horns in modern musk oxen,...
holotype, a name-bearing specimen. The same abstract named Type C as Achelousaurus horneri. In 1995, Sampson published a larger article, indicating the...
Rubeosaurus (now seen as a synonym of Styracosaurus), Einiosaurus, and Achelousaurus were discovered in. Originally proposed as a distinct taxon in 1992...
include Pachyrhinosaurus, Avaceratops, Einiosaurus, Albertaceratops, and Achelousaurus. The cladogram presented below represents a phylogenetic analysis by...
large variety of ceratopsians coexisted in this region, which included Achelousaurus, Brachyceratops, Cerasinops, Einiosaurus, Prenoceratops and Rubeosaurus...
"roof" in front of much of the nasal cavity, similar to Centrosaurus and Achelousaurus. There is a spine formed by the nasal and premaxilla, as is typical...
capture him and he activates his Achelousaurus. Ursula unleashes Spiny upon it, who doesn't do a good job on the Achelousaurus (in the Dinosaur King gameplay...
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