Chasmosaurus
From Greek chasma meaning 'opening/hollow/gulf' and Greek sauros meaning 'lizard'. Full meaning: 'opening lizard', referring to the large fenestrae (openings) in its frill.
Chasmosaurus is a genus of ceratopsid dinosaur from the Late Cretaceous Period in North America. Its given name means 'opening lizard', referring to the large openings (fenestrae) in its frill (Greek chasma, meaning 'opening', 'hollow', or 'gulf'; and sauros, meaning 'lizard'). With a length of 4.3-4.8 meters (14.1-15.7 ft) and a weight of 1.5-2 tonnes (1.7-2.2 short tons)-or anywhere from 2,200 to nearly 5,000 lbs-Chasmosaurus was of a slightly smaller to "average" size, especially when compared to larger ceratopsids (such as Triceratops, which were about the size of an African bush elephant).
Diagnosis
- Skull broadly triangular in superior aspect with a narrow, abbreviated facial portion and a broad, greatly extended posterior crest ending squarely behind
- Coalesced parietals forming a slender framework enclosing large sub-triangular fontanelles so large as to reduce posterior two-thirds of parietals to a mere slender framework
- Squamosals very long and narrow with a scalloped free border bearing low sub-conical epoccipitals
- Postfrontal fontanelle present, long and narrow, extending between the supraorbital horn-cores
- Supraorbital horn-cores small and upright, broadly oval in cross section near the base with greater diameter fore and aft
- Parietal crest remarkably flat, extending backward and laterally in almost a horizontal plane, with length to breadth ratio approximately 7 to 8
Species
Chasmosaurus belli (Lambe, 1902)
Type species
First named as Monoclonius belli
Named for collector Walter Bell, from whose discovery area the holotype parietal bone was recovered.
- Holotype
- NMC 491 , Canadian Museum of Nature
- Material
- Part of the coalesced parietals of the frill.
- Horizon
- Belly River Group, Campanian, Late Cretaceous , 83.6–72.2 million years ago
- Locality
- Red Deer River, between Berry Creek and Dead Lodge Cañon, Alberta, Canada Lambe (1902) gives the type only as "from Red Deer river", from collections made in the Belly River series between Berry Creek and Dead Lodge Cañon; no source read places it in the Oldman or the Dinosaur Park Formation.
Synonyms
-
Protorosaurus belli reassigned
In January 1914 Lambe moved Monoclonius belli to his new genus Protorosaurus; the name was preoccupied, and the next month he replaced it with Chasmosaurus.
Synonyms of the genus
| Name | Type | Reason |
|---|---|---|
| Eoceratops | junior subjective | Originally described as Monoclonius canadensis and later re-erected as Eoceratops; the material is now treated as morphological variation within Chasmosaurus. |
| Mojoceratops | junior subjective | Initially synonymized with Chasmosaurus based on overlapping diagnostic features; recent fieldwork in Dinosaur Provincial Park suggests Mojoceratops may yet prove to be a valid genus. |
| Protorosaurus | preoccupied | Lambe's (1914) first name for the genus, preoccupied by the earlier reptile genus Protorosaurus of von Meyer; Lambe replaced it with Chasmosaurus the next month. |
References
-
Lambe, L. M. (1902). New genera and species from the Belly River Series (mid-Cretaceous). Geological Survey of Canada Contributions to Canadian Palaeontology 3(2): 25-81. doi:10.5281/zenodo.3233762
Names the species, as Monoclonius belli, on the coalesced parietals of a frill from the Red Deer River.
lambe1902a -
Lambe, L. M. (1914). On the fore-limb of a carnivorous dinosaur from the Belly River Formation of Alberta, and a new genus of Ceratopsia from the same horizon, with remarks on the integument of some Cretaceous herbivorous dinosaurs. The Ottawa Naturalist 27(10): 129-135.
Proposes Protorosaurus for Monoclonius belli.
lambe1914c -
Lambe, L. M. (1914). On Gryposaurus notabilis, a new genus and species of trachodont dinosaur from the Belly River Formation of Alberta, with a description of the skull of Chasmosaurus belli. The Ottawa Naturalist 27(11): 145-155.
Replaces the preoccupied Protorosaurus with Chasmosaurus.
lambe1914b -
Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.
Source of the appearance features.
paul2024a