Omnisaura
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Dinosaur genus

Achelousaurus

Sampson 1994

Achelousaurus is a dinosaur genus known from bones, found in rocks 83.6–72.2 million years old, in the United States.

Also calledja アケロウサウルスzh 河神龍
mediummedium: Only Wikidata gives this; nothing contradicts it.
Confidence labels
How sure are we?0 high8 medium2 lowHow we rate confidence

Confidence labels are switched off. Facts with low confidence, or where sources disagree, still carry a small dot: tap it for the reason.

At a glance

Data as of 12 October 2026
83.6–72.2 Ma
Triassic
Jurassic
Cretaceous
252 million years ago20114366

The last non-bird dinosaurs died out 66 million years ago. That's as far from us as the end of this bar.

Named by
Sampson 1994
disputedlow: Sources disagree and an editor has not ruled yet.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Described in
S. D. Sampson (1994). Two new horned dinosaurs (Ornithischia: Ceratopsidae) from the Upper Cretaceous Two Medicine Formation, Montana, USA. Journal of Vertebrate Paleontology 14(3, suppl.): 44A.
mediummedium: Only PBDB gives this; its author and year match the naming authority (Sampson 1994).
Sources

Given by: Paleobiology Database. The publication the Paleobiology Database gives as the authority for this genus name, usually the one that first named and described it.

Type species
Achelousaurus horneri
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Lived
Campanian, 83.6–72.2 million years ago
mediummedium: Only PBDB gives this; nothing contradicts it.
Omnisaura calculation83.6–72.2 million years ago, from its dated fossil records
lowlow: Omnisaura's calculation from only 2 dated record(s).
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Fossils found in
United States
mediummedium: Only PBDB records it (2 records).
Sources

Given by: Paleobiology Database. How it was chosen: Union of all sources (ISO 3166).

Rock formations
Two Medicine
mediummedium: Only PBDB records it (2 records).
Sources

Given by: Paleobiology Database. How it was chosen: Canonical names, automatic and editor-approved matches applied.

Family
Ceratopsidae
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Parent group
Pachyrhinosaurini
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Known from
Bones
Sources

Given by: Paleobiology Database (what the name was based on).

Sources: Paleobiology Database (CC BY 4.0), Wikidata (CC0 1.0)Confidence levels and gaps are Omnisaura's own assessment.

Gaps are answers

What isn't known yet

  • Order: no source we use gives it yet.
  • What it was named after: no source we use gives it yet.
  • Resting on one source: 5 facts come from a single source with nothing against them (rated medium): type species (PBDB); parent group (PBDB); family (PBDB); age (headline) (PBDB); common names (Wikidata).

Size, diet and behaviour aren't covered yet. Omnisaura leaves them out rather than guess.

Where sources disagree

1 open

Authority

  • Sampson 1994PBDB (shown above)
  • Scott D. Sampson, 1995Wikidata

The sources give different values. An editor hasn't ruled yet, so this is rated low until they do.

Did it meet…?

?

Same time, different places. Their fossils overlap in age, 83.6 to 72.2 million years ago, but no rock formation holds both.

Going by the ages and rock formations of their dated fossils, as on the map. Compare their fossil sites on the map.

Lived alongside

Genera found in the same rock formations, from rocks of the same age.

HypacrosaurusDaspletosaurusMaiasauraOohkotokiaOrodromeusTroodonBrontotholusPrismatoolithusProsaurolophusSaurornitholestesSpheroolithusCerasinopsContinuoolithusEiniosaurusEuoplocephalusGryposaurusand 12 more

Same family

Other genera in Ceratopsidae with a full profile.

AgujaceratopsAlbertaceratopsAnchiceratopsArrhinoceratopsAvaceratopsBisticeratopsBravoceratopsCentrosaurusCeratopsipesChasmosaurusCoahuilaceratopsCoronosaurusCrittendenceratopsDiabloceratopsEiniosaurusKosmoceratopsand 9 more

Credits

Where this page comes from

  • Paleobiology DatabaseCC BY 4.0 · fossil records, ages, classification
  • WikidataCC0 1.0 · names and identifiers
  • OmnisauraOmnisaura editorial · confidence levels and gaps
  • PaleoMAP PaleoCoastlines (Kocsis and Scotese 2021)CC BY 4.0 · ancient coastlines on the small map
  • Natural EarthPublic domain · today's coastlines