Cretaceous
Monoclonius
Monoclonius crassus
The catalogue presents Monoclonius as a herbivore member of Ceratopsidae that lived during the Cretaceous, between 77.0–75.0 Ma. Its estimated range is 5.5 m in length and 1.0–1.5 t in mass, giving a practical sense of scale. Reference material comes from Judith River Formation, Montana, USA. Size and mass are approximations and may change with new fossils or methods.
Evidence-backed summary
For Monoclonius, the PBDB records the taxonomic attribution as Cope (1876).
The PBDB places it in Centrosaurinae, and the catalogue record assigns it to the family Ceratopsidae.
- PBDB · taxon.parent
- Ceratopsidae
In the PBDB record, the reported stratigraphic range is the Campanian.
The PBDB catalogues 2 occurrences, with material from the Judith River Formation (1) and from the Oldman Formation (1). Provenance: United States and Canada.
The catalogue records the holotype as CMN 8790 and the type locality as “Judith River Formation, Montana, USA”.
- CMN 8790
- Judith River Formation, Montana, USA
The catalogue's reference measurements are 5.5 m in length and 1.0–1.5 t in mass — estimates, which vary with specimen and method.
- 5.5 m
- 1.0-1.5 tons
The record gathers 65 bibliographic references registered in the PBDB, listed below.
Where it lived
Fossil occurrences on today’s map and in the tectonic reconstruction.
Positions reconstructed by PBDB/GPlates, not observed; this is not an exact habitat map.
Artistic 3D reconstruction
There is no approved species-specific 3D model yet. Generic anatomy will not be presented as if it were evidence.
Physical Specifications
- Length
- 5.5 m
- Weight
- 1.0–1.5 t
- Period
- Cretaceous
- Time range
- 77.0–75.0 Ma
Discovery Information
- First Discovery
- 1876
- Described by
- Edward Drinker Cope
Taxonomic Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Reptilia
- Order
- Ornithischia
- Family
- Ceratopsidae
- Genus
- Monoclonius
- Species
- M. crassus
Data status
Taxonomic name matched to PBDB and checked on 2026-08-08.
Taxonomic linkage does not automatically validate size, mass, behaviour or appearance.
- Type specimen
- CMN 8790
- Type locality
- Judith River Formation, Montana, USA