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CretaceousherbivoreFossil completeness: excellent

Chasmosaurus belli

Pronunciation: KAZ-moh-SORE-us BELL-eye

A classic long-frilled horned dinosaur from Alberta, known from complete skulls, articulated skeletons, skin impressions and a rare juvenile skeleton.

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Chasmosaurus belli

The page URL and title are included automatically. Optional contact details are used only to discuss this report. Do not submit private information or precise sensitive fossil-site coordinates.

Last updated 16 July 2026

Chasmosaurus belli browsing in a Dinosaur Park Formation forestArt by J. T. Csotonyi · CC BY 2.5

Field guide

Overview

Chasmosaurus belli was a medium-sized chasmosaurine ceratopsid from the Dinosaur Park Formation of Alberta. Its long, low frill was pierced by two enormous openings, greatly reducing the weight of the skull while leaving a broad visual display surface. The species is represented by skulls, articulated skeletons and skin impressions, including CMN 2245 at about 4.7 metres long. Chasmosaurus taxonomy has a complicated history: the distinction between C. belli and material traditionally called C. russelli rests on subtle frill geometry, and several historically named species have moved to other genera.

Its fossils occur between approximately 76.5 and 75.3 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Form and function

Anatomy

A narrow parrot-like beak cropped vegetation, while batteries of continually replacing cheek teeth sliced it. The nasal horn was short, and brow horns ranged from modest points to strongly reduced structures in mature individuals. The long frill expanded behind the skull with two large parietal openings and small bony ornaments around its edge. Robust forelimbs, broad hands and powerful hind limbs supported a barrel-shaped quadrupedal body. Skin associated with CMN 2245 preserves non-overlapping scales of several sizes around the shoulder and pelvis.

  • Long frill pierced by two very large openings
  • Short nasal horn and variably developed brow horns
  • Small epiossifications around the edge of the frill
  • Narrow beak backed by dense dental batteries
  • Robust four-legged body and powerful neck
  • Directly preserved skin with several scale sizes

Evolutionary position

Scientific classification

  1. 1Dinosauriaclade
  2. 2Ornithischiaclade
  3. 3Neornithischiaclade
  4. 4Marginocephaliaclade
  5. 5Ceratopsiaclade
  6. 6Ceratopsoideaclade
  7. 7Ceratopsidaefamily
  8. 8Chasmosaurinaesubfamily
  9. 9Chasmosaurusgenus
  10. 10Chasmosaurus bellispecies

This simplified classification path shows one placement from Dinosauria to this species. Each step is clickable, and other analyses may support alternative relationships.

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Scale

Size comparison

Scientific record

Discovery and naming

Lawrence Lambe collected the type frill bone, CMN 491, at Berry Creek in Alberta in 1898. In 1902 he named it Monoclonius belli, honouring collector Walter Bell. More complete skulls found by Charles H. Sternberg and his sons in 1913 showed that it belonged to a distinctive long-frilled animal. Lambe established a separate genus in 1914; an initial name, Protorosaurus, was already occupied, so he replaced it with Chasmosaurus. Later skeletons such as CMN 2245 and ROM 843 revealed nearly the whole body.

Discovery credit: Lawrence M. Lambe, Geological Survey of Canada.

Naming authors: Lawrence M. Lambe.

Palaeoenvironment

Habitat and behaviour

The Dinosaur Park Formation records rivers, floodplains, ponds and coastal wetlands beside the Western Interior Seaway. Chasmosaurus browsed flowering plants, conifers and ferns alongside hadrosaurs, armoured dinosaurs and short-frilled ceratopsids. Gorgosaurus and Daspletosaurus were major predators. The formation spans enough time that its full species list should not be treated as one unchanging community.

The frill and horns likely combined display, recognition and physical protection, but their exact role cannot be isolated from bone alone. Large frill openings make it unlikely that the structure functioned simply as a solid shield. Changes in brow horns and frill shape through growth show that appearance altered substantially with age. Unlike Centrosaurus, Chasmosaurus is not known from enormous single-species bonebeds, so claims of giant permanent herds are unsupported.

Worth knowing

Field notes

  • Its name refers to the huge openings in the frill.
  • The first fossil was only part of the frill and was originally placed in Monoclonius.
  • CMN 2245 preserves extensive patches of original skin around the shoulder and pelvis.
  • A rare juvenile skeleton shows that the frill became proportionally broader and more elaborate during growth.

Fossil distribution

Fossil locations

Berry Creek and Dinosaur Provincial Park fossil regionBerry Creek and Dinosaur Provincial Park fossil region, Red Deer River badlands, Alberta, Canada
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Berry Creek and Dinosaur Provincial Park fossil region

Red Deer River badlands, Alberta, Canada

Dinosaur Park Formation

regional marker

Markers are deliberately approximate. They identify published fossil areas without exposing sensitive excavation coordinates.

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Fossil specimen record

Museums and research collections

Canadian Museum of Nature

verified

Gatineau, Quebec, Canada

Repository of the original partial frill that defines Chasmosaurus belli and of the nearly complete skeleton CMN 2245. The research collection is separate from the public museum galleries.

Record type: partial originalChecked 16 July 2026Institution website

Royal Ontario Museum

historical

Toronto, Ontario, Canada

Repository associated with one of the best-known Chasmosaurus belli skulls and skeletons. The pictured mount has been displayed at the Royal Tyrrell Museum; ownership and display location should not be conflated.

Record type: originalInstitution website

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

Scientific uncertainty

  • The boundary between C. belli, C. russelli and indeterminate Chasmosaurus specimens remains sensitive to frill characters and specimen maturity.
  • The holotype CMN 491 is only a partial parietal, so later referred skeletons supply most body information.
  • Horn and frill proportions change with growth and vary among individuals.
  • The foreground reconstruction image comes from a multi-species palaeoecological scene rather than an isolated model.
  • Body-mass estimates vary because relatively complete skeletons still require reconstructed soft-tissue volumes.

Evidence

References and sources

  1. 01
    Palaeobiology Collections

    Canadian Museum of Nature

    Open source
  2. 02
    New genera and species from the Belly River Series

    Lawrence M. Lambe · Contributions to Canadian Palaeontology 3(2) · 1902

    Open source
  3. 03
    A re-evaluation of the chasmosaurine ceratopsid genus Chasmosaurus from the Upper Cretaceous Dinosaur Park Formation of western Canada

    James A. Campbell, Michael J. Ryan, Robert B. Holmes, Claudia J. Schröder-Adams · PLOS ONE 11(1), e0145805 · 2016

    Open source