| Diet | Herbivore |
| Height | 2m |
| Length | 4.8m |
| Weight | 2 tonnes |
| Environment | Land |
| Era | Cretaceous |
| Period | Late Cretaceous |
| Type | Ceratopsian |
| Location | North America |
Chasmosaurus was a remarkable ceratopsian dinosaur that lived in North America during the Late Cretaceous period, approximately 83.6 million years ago. Its name, meaning 'opening lizard', perfectly describes its most distinctive feature—a spectacular neck frill containing large window-like openings called fenestrae. These enormous holes in the bone made the frill much lighter whilst maintaining its impressive size for display purposes.
Measuring between 4.3 and 4.8 metres in length and weighing 1.5 to 2 tonnes, Chasmosaurus was moderately sized compared to other ceratopsians. Like all members of its group, it walked on four sturdy legs and possessed the characteristic three-horned face, though Chasmosaurus had relatively modest horns compared to later ceratopsians like Triceratops. Its beak-like mouth was perfectly adapted for cropping tough vegetation.
As a herbivore, Chasmosaurus used its sharp beak to slice through ferns, cycads, and early flowering plants that grew in the warm, humid forests of Late Cretaceous North America. Its impressive frill likely served multiple purposes: attracting mates, intimidating rivals, and possibly helping to regulate body temperature. The colourful patterns that may have decorated this frill would have made Chasmosaurus a truly spectacular sight.
Chasmosaurus lived in herds across the river plains and coastal forests of what is now Alberta, Canada, and parts of the western United States. These social dinosaurs shared their environment with fearsome predators like Albertosaurus, making their impressive frills and group behaviour essential for survival.
Chasmosaurus had an enormous rectangular neck frill with distinctive large rectangular and triangular openings (fenestrae) that made it appear almost lace-like. Its face bore three horns—two modest brow horns above the eyes and a smaller nasal horn—along with the typical ceratopsian parrot-like beak.
Chasmosaurus likely lived in herds for protection against predators, using visual displays with their colourful frills to communicate with other members of their species. During mating season, males probably engaged in head-butting contests and frill displays to compete for females, similar to modern horned animals.
Chasmosaurus has appeared in several dinosaur documentaries and educational programmes, though it's less famous than its cousin Triceratops.
| Phylum | Chordata |
| Class | Ornithischia |
| Family | Ceratopsidae |
| Genus | Chasmosaurus |
Chasmosaurus was first described by Lawrence Lambe in 1914. The original fossils were discovered at Alberta, Canada.
