Chasmosaurus belli

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.

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

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.

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.

• 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.

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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