EXPLORE PREHISTORY 220 prehistoric animal profiles · Scientific & movie-style image galleries
DinoGrove.
The collection/Avaceratops

EXHIBIT 194

Avaceratops

Avaceratops lammersi

Avaceratops is known securely from an immature skeleton, making the adult appearance particularly difficult to establish. [5]

Evidence profile

TWO WAYS TO PICTURE THE PAST

Compare the evidence with the familiar movie image. The illustrations are not to a shared scale.

01 / FOSSIL VIEW

The evidence in the bones

Avaceratops squamosal bone with a marked ridge and prominences.

Photographed Avaceratops squamosal, a side-frill bone, cropped from the original comparative figure. Red lines and arrows mark bone features, not living coloration. The image does not supply missing adult horns or a complete frill reconstruction. [2]

Avaceratops squamosal.png · Héctor E. Rivera-Sylva, Brandon P. Hedrick and Peter Dodson. CC BY 4.0. Proportional resizing and WebP conversion; no anatomy edits. Current Commons composition preserved.

The photograph or figure shows the credited fossil material; displayed mounts and labels can include interpretation.

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Illustrative reconstruction of Avaceratops; colors, soft tissues and missing anatomy remain interpretive.

Original cinematic interpretation of Avaceratops. This depicts a conditional immature-type reconstruction. The unpreserved nasal and brow regions, whole body and covering are comparative; it does not combine the type with the disputed larger skull MOR692. Lighting, colors and scenery are artistic choices; this image does not document directly observed behavior. Lighting, coloration and scenery are artistic choices. This image does not document a fossil locality or behavior.

Original artwork · artistic interpretation.

Scientific view: source-informed reconstruction, credited paleoart or specimen-based imagery. Movie-style view: Original artistic interpretation. Reconstructions involve uncertainty.

PERIODLate Cretaceous[1]
DIETHerbivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDMontana, USA[1]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Avaceratops

Avaceratops comes from the Careless Creek Quarry in Montana, where sandy river deposits preserved its remains. Researchers compare the rock layers with the Judith River Formation's wider sequence to place the discovery in context. That correlation has uncertainties, so the quarry's location is more secure than a highly precise date for the individual dinosaur. [D4]

The original specimen was immature. Its frill and other skull features therefore need to be read as the anatomy of a growing animal. Features can change with age, making it risky to treat every juvenile difference as a permanent adult characteristic. Comparative research also cautions that incomplete frill bones cannot securely show whether openings were absent in the complete, mature structure. [D8]

The Natural History Museum identifies Avaceratops as a plant eater and lists a length of about 2.3 metres. That is a reference figure without a stated specimen, calculation or growth stage. It should not quietly become a maximum adult length. The known young individual still leaves questions about adult appearance and size. [D3]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

The animal, the evidence, and the questions still open.

Bone histology shows active growth. A short frill in a young animal cannot automatically define its adult ornamentation. [D5] [D2]

Profile scope: A. lammersi, chiefly immature holotype ANSP 15800; MOR 692 is excluded from secure adult reference measurements. [D2]

Time
Late Cretaceous
Fossil locations in this exhibit
Montana, USA
How to read the evidence

Source supported identifies a description documented by the cited source. Inferred marks a reconstruction or functional estimate. Debated marks competing interpretations. Not established means the sources reviewed for this dossier do not support a firm conclusion; it does not mean a behavior never occurred.

A size reference is an estimate, not a population range. Nesting evidence does not by itself establish courtship, mate choice, or lifelong pairing.

Length

Inferred

About 2.3 m; museum reference

Educational estimate with unspecified specimen and method. The secure type is immature; this does not establish mature size. [D3] [D5]

Body mass

Not established

Not established here

No inspected mass model securely tied to the immature type was located. Uncertain adult MOR 692 is not substituted. [D2]

Diet

Inferred

Plant eater

Museum herbivory assignment; the reviewed evidence does not identify an exact menu or preserved meal. [D3]

Time and habitat

Inferred

Campanian; Montana river deposits

Careless Creek Quarry, Judith River Formation; likely lower McClelland Ferry Member. Local bed-age correlation remains imperfect. [D4]

Locomotion

Inferred

Four-legged body plan

Ceratopsid posture inferred comparatively; genus-specific trackways, gait and speed are not established here. [D7]

Distinctive anatomy

Source supported

Short frill in an immature individual

The type lacks frill epimarginals, potentially a juvenile feature. Incomplete parietals make permanently absent adult windows uncertain. [D2]

Reproduction & life together

Reproduction and life cycle

Not established

Not established here

ANSP 15800 was juvenile or young subadult with rapidly growing bone. Its growth stage does not establish breeding age, nests or parental care. [D5]

Mating and courtship

Not established

Not established here

Ceratopsian sexual-selection hypotheses are comparative. Ornament shape does not establish this genus’s mate choice, courtship sequence or sex-specific roles. [D6]

Social behavior

Not established

Not established here

A partial type skeleton and uncertain adult skull association do not establish a living herd, social organization or solitary habits. [D1] [D2]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. The morphology and systematics of Avaceratops, a primitive horned dinosaur from the Judith River Formation (Late Campanian) of Montana, with the description of a second skullJournal of Vertebrate Paleontology; Penkalski and Dodson (1999) · Accessed 2026-10-02Original abstract and author-uploaded article cover inspected. Type partial skeleton and frill traits; 4.2 m adult reconstruction depends on a second skull referral challenged later. Full descriptive text inaccessible. · Inspected: abstract
  2. A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, CanadaCanadian Journal of Earth Sciences; Ryan, Holmes, Mallon, Loewen and Evans (online 2016; issue 2017) · Accessed 2026-10-02Indexed original discussion excerpt inspected: juvenile type has weak diagnostic utility; no definitive MOR 692 referral without ontogenetic intermediates; incomplete parietals cannot securely establish fenestra absence. Full article inaccessible. · Inspected: excerpt
  3. AvaceratopsNatural History Museum, London · Accessed 2026-10-02Institutional directory inspected: 2.3 m educational reference and herbivory, with no specimen/method/maturity designation. · Inspected: page
  4. Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USAPLOS ONE; Mallon and colleagues (2016) · Accessed 2026-10-02Original full paper locality section inspected: Avaceratops type at Careless Creek Quarry, sandy fluvial deposits, likely lower McClelland Ferry Member; age correlation remains uncertain. · Inspected: page
  5. Filling in Gaps in the Ceratopsid Histologic Database: Histology of Two Basal Centrosaurines and an Assessment of the Utility of Rib Histology in the CeratopsidaeThe Anatomical Record; Hedrick and colleagues (online 2019; issue 2020) · Accessed 2026-10-02Original full publisher text inspected: ANS 15800 juvenile/young subadult, growth and rib remodeling. Kosmoceratops/Utahceratops comparisons summarize Levitt 2013; that thesis was not independently accessed. · Inspected: page
  6. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolutionProceedings of the Royal Society B; Knapp, Knell, Farke, Loewen and Hone (2018) · Accessed 2026-10-02Original full text inspected. Comparative ornament-divergence analysis; sexual-selection hypothesis is not a directly observed mating behavior or identified sex. · Inspected: page
  7. Osteological correlates for quadrupedality in ornithischian dinosaursActa Palaeontologica Polonica; Maidment and Barrett (2014) · Accessed 2026-10-02Original full paper inspected. Ceratopsidae treated as quadrupedal within herbivorous Ornithischia; application to skull-only taxa is explicitly comparative. · Inspected: page
  8. A Centrosaurine (Dinosauria: Ceratopsia) from the Aguja Formation (Late Campanian) of Northern Coahuila, MexicoPLOS ONE; Rivera-Sylva, Hedrick and Dodson (2016) · Accessed 2026-10-02Original full text and Figure 14 comparative Avaceratops squamosal inspected. ANS 15800 juvenile features and fenestra uncertainty; later 2017 referral critique takes precedence. · Inspected: page

THE STORY IN THE FOSSILS

A young dinosaur and an uncertain adult

An older 4.2 m adult reconstruction relied on the second skull MOR 692. The later assessment requires intermediate growth stages before that skull can securely define adult Avaceratops. [1] [2]

The sampled type’s ribs are heavily remodeled. Histological work cautions that rib growth marks can be poor chronological records, so a missing annual line cannot establish age. [5]

A note on scale and time

The dossier identifies the scope of each reference estimate. A mount, an individual fossil and a species-wide adult range are different measurements. Comparison metrics remain unavailable where adult scope has not been established. Unknown does not mean zero.

Sources & editorial notes

Sources support the stated claims and scopes. Refer to the evidence notes for uncertainty.

  1. The morphology and systematics of Avaceratops, a primitive horned dinosaur from the Judith River Formation (Late Campanian) of Montana, with the description of a second skullJournal of Vertebrate Paleontology; Penkalski and Dodson (1999) · Accessed 2026-10-02Original abstract and author-uploaded article cover inspected. Type partial skeleton and frill traits; 4.2 m adult reconstruction depends on a second skull referral challenged later. Full descriptive text inaccessible. · Inspected: abstract
  2. A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, CanadaCanadian Journal of Earth Sciences; Ryan, Holmes, Mallon, Loewen and Evans (online 2016; issue 2017) · Accessed 2026-10-02Indexed original discussion excerpt inspected: juvenile type has weak diagnostic utility; no definitive MOR 692 referral without ontogenetic intermediates; incomplete parietals cannot securely establish fenestra absence. Full article inaccessible. · Inspected: excerpt
  3. AvaceratopsNatural History Museum, London · Accessed 2026-10-02Institutional directory inspected: 2.3 m educational reference and herbivory, with no specimen/method/maturity designation. · Inspected: page
  4. Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USAPLOS ONE; Mallon and colleagues (2016) · Accessed 2026-10-02Original full paper locality section inspected: Avaceratops type at Careless Creek Quarry, sandy fluvial deposits, likely lower McClelland Ferry Member; age correlation remains uncertain. · Inspected: page
  5. Filling in Gaps in the Ceratopsid Histologic Database: Histology of Two Basal Centrosaurines and an Assessment of the Utility of Rib Histology in the CeratopsidaeThe Anatomical Record; Hedrick and colleagues (online 2019; issue 2020) · Accessed 2026-10-02Original full publisher text inspected: ANS 15800 juvenile/young subadult, growth and rib remodeling. Kosmoceratops/Utahceratops comparisons summarize Levitt 2013; that thesis was not independently accessed. · Inspected: page
  6. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolutionProceedings of the Royal Society B; Knapp, Knell, Farke, Loewen and Hone (2018) · Accessed 2026-10-02Original full text inspected. Comparative ornament-divergence analysis; sexual-selection hypothesis is not a directly observed mating behavior or identified sex. · Inspected: page
  7. Osteological correlates for quadrupedality in ornithischian dinosaursActa Palaeontologica Polonica; Maidment and Barrett (2014) · Accessed 2026-10-02Original full paper inspected. Ceratopsidae treated as quadrupedal within herbivorous Ornithischia; application to skull-only taxa is explicitly comparative. · Inspected: page
  8. A Centrosaurine (Dinosauria: Ceratopsia) from the Aguja Formation (Late Campanian) of Northern Coahuila, MexicoPLOS ONE; Rivera-Sylva, Hedrick and Dodson (2016) · Accessed 2026-10-02Original full text and Figure 14 comparative Avaceratops squamosal inspected. ANS 15800 juvenile features and fenestra uncertainty; later 2017 referral critique takes precedence. · Inspected: page

FOLLOW YOUR CURIOSITY

Who will you meet next?

KEEP EXPLORING

More from the collection