Chasmosaurus

Chasmosaurus was a classic horned dinosaur that gave its name to the chasmosaurine subfamily. Discovered in Alberta, Canada, this herbivore lived approximately 76 million years ago during the Late Cretaceous. It reached lengths of nearly 5 metres and weighed about 2 tonnes, roughly the size of an adult rhinoceros. Its name refers to the broad, heart-shaped neck frill, which possessed immense fenestrae, or hollow openings, making the structure remarkably light for its surface area. The frill was bordered by small, pointed osteoderms and was probably vivid in life, serving for species identification or mating displays rather than physical defence. Chasmosaurus had modest brow horns and a blunt nasal horn. Exceptionally preserved skin impressions have revealed large, non-overlapping polygonal scales interspersed with circular, dome-shaped tubercles across its flanks.

Its expansive neck frill featured enormous openings that significantly reduced its skull weight.

Where and when

Chasmosaurus lived in the Late Cretaceous, from 76.5 to 75 million years ago (Campanian age). Its remains come from Canada, in the Dinosaur Park Formation.

The numbers

Length 4.8 m (estimates run from 4.5 to 5 m). Mass about 1.9 t. Hip height about 1.7 m. That is 2.8 human-lengths, or 0.43 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

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