The basis for the whole chasmosaur grouping of the ceratopsids, Chasmosaurus (“chasm lizard”) lived about 76-75 million years ago in Alberta, Canada. Two different species are currently recognized within the genus, with the smaller C. russeli found in older rock layers and the type species C. belli being slightly younger.
Many different fossils are known, including a juvenile, with C. belli adults reaching a size of around 4.8m (15’8”). Different individuals display a lot of variation in their ornamentation, especially in the size and curve of their brow horns – and some specimens even lost their brow horns completely, with the bony cores being resorbed with age.
It shared its habitat with its distant relative Centrosaurus, but since Chasmosaurus had a longer narrower snout than its centrosaur cousin it probably fed on different types of vegetation.
Skin impressions are also known from around the right hip region on one specimen, showing large scales in spaced-out horizontal rows among much smaller scales.