Chasmosaurus

Chasmosaurus Temporal range: Late Cretaceous (Campanian), 77–76 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
C. belli skeleton, Royal Ontario Museum specimen 843
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Family:	†Ceratopsidae
Subfamily:	†Chasmosaurinae
Genus:	†Chasmosaurus Lambe, 1914
Species
†C. belli (Lambe, 1902) [originally Monoclonius belli, type] †C. russelli Sternberg, 1940 †C. irvinensis? Holmes et al., 2001
Synonyms
Eoceratops Lambe, 1915 Mojoceratops Longrich, 2010 Vagaceratops? Sampson et al., 2010

Chasmosaurus (/ˌkæzmoʊˈsɔːrəs/ KAZ-moh-SOR-əs) 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 metres (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., give or take—Chasmosaurus was of a slightly smaller to ‘average’ size, especially when compared to larger ceratopsians (such as Triceratops, which were about the size of an African bush elephant).

It was initially to be called Protorosaurus, but this name had been previously published for another animal. All of the excavated specimens of Chasmosaurus were collected at the Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Referred specimens of C. russelli come from the lower beds of the formation, while C. belli comes from the middle and upper beds.^[1]