page_title: Chasmosaurus
section_title: Discovery and species
hierarchical_section_title: Chasmosaurus / Discovery and species
caption_attribution_description: English: George F. Sternberg preparing the skull of Chasmosaurus belli. Title: Hunting dinosaurs in the bad lands of the Red Deer River, Alberta, Canada; a sequel to The life of a fossil hunter Identifier: cu31924012130021 (find matches) Year: 1917 (1910s) Authors: Sternberg, Charles H. (Charles Hazelius), b. 1850 Subjects: Paleontology; Dinosaurs Publisher: Lawrence, Kan. , C. H. Sternberg Contributing Library: Cornell University Library Digitizing Sponsor: MSN View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: ' Text Appearing After Image: ' Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
context_page_description: Chasmosaurus is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings in its frill. With a length of 4.3–4.8 metres and a weight of 1.5–2 tonnes, Chasmosaurus was a ceratopsian of average size. Like all ceratopsians, it was purely herbivorous. It was initially to be called Protorosaurus, but this name had been previously published for another animal. All specimens of Chasmosaurus were collected from the Dinosaur Park Formation of the Dinosaur Provincial Park of Alberta, Canada. C. russelli comes from the lower beds of the formation while C. belli comes from middle and upper beds.
context_section_description: In 1898, Lawrence Morris Lambe of the Geological Survey of Canada made at the Berry Creek the first discovery of Chasmosaurus remains, holotype NMC 491, a parietal bone that was part of a neck frill. Although recognizing that his find represented a new species, Lambe thought this could be placed in a previously-known short-frilled ceratopsian genus: Monoclonius. He erected the new species Monoclonius belli to describe his findings. The specific name honoured collector Walter Bell.
  However, in 1913, Charles Hazelius Sternberg and his sons found several complete "M. belli" skulls in the middle Dinosaur Park Formation of Alberta, Canada. Based on these finds, Lambe (1914) erected Protorosaurus ("before Torosaurus), but that name was preoccupied by the Permian reptile Protorosaurus, so he subsequently created the replacement name Chasmosaurus in February 1914. The name Chasmosaurus is derived from Greek χάσμα, khasma, "opening" or "divide" and refers to the very large parietal fenestrae in the skull frill. Lambe now also assigned a paratype, specimen NMC 2245 found by the Sternbergs in 1913 and consisting of a largely complete skeleton, including skin impressions. 
  Since that date, more remains, including skulls, have been found that have been referred to Chasmosaurus, and several additional species have been named within the genus. Today some of these are considered to only reflect a morphological variation among the known sample of Chasmosaurus belli skulls; others are seen as valid species of Chasmosaurus or as separate genera. In 1933 Barnum Brown named Chasmosaurus kaiseni, honouring Peter Kaisen and based on skull AMNH 5401, differing from C. belli in having very long brow horns. This form is perhaps related to Chasmosaurus canadensis ('from Canada') named by Thomas M. Lehman in 1990. The latter species, originally Monoclonius canadensis Lambe 1902, had been described as Eoceratops canadensis by Lambe in 1915. Eoceratops and the long-horned Chasmosaurus kaiseni were thought to probably be exemplars of Mojoceratops by Nicholas Longrich, although different teams of researchers have found Mojoceratops to be a synonym of Chasmosaurus russelli. Campbell and colleagues, in their 2016 analysis of Chasmosaurus specimens found Eoceratops and C. kaiseni to be referable to Chasmosaurus sp. due to the lack of the parietal preserved in the holotypes of both. Richard Swann Lull in 1933 named an unusual, short-muzzled skull, specimen ROM 839 (earlier ROM 5436) collected in 1926, as Chasmosaurus brevirostris, "with a short snout". This has been seen as a junior synonym of C. belli. 
  Charles Mortram Sternberg added Chasmosaurus russelli in 1940, based on specimen NMC 8800 from southwestern Alberta (lower Dinosaur Park Formation). The specific name honours Loris Shano Russell. In 1987, Gregory S. Paul renamed Pentaceratops sternbergii into Chasmosaurus sternbergi, but this has found no acceptance. In 2000, George Olshevsky renamed Monoclonius recurvicornis Cope 1889 into Chasmosaurus recurvicornis as its fossil material is likely chasmosaurine; this is a nomen dubium. Thomas Lehman described Chasmosaurus mariscalensis in 1989 from Texas, which has now been renamed Agujaceratops. 
  The most recently described species is Chasmosaurus irvinensis named in 2001, which stems from the uppermost beds of the Dinosaur Park Formation. This species was given its own genus, Vagaceratops, in 2010. However, Campbell et al. (2019) referred Vagaceratops back to Chasmosaurus.  As Fowler and Fowler found Vagaceratops likely to be the sister taxon of Kosmoceratops in 2020, they suggested it should be maintained as a distinct genus from Chasmosaurus, as its placement would proably remain unstable until chasmosaurines are better understood.
  The species Mojoceratops perifania was based on holotype specimen TMP 1983.25.1 consisting of a partial skull including the parietal and from the paratypes TMP 1999.55.292, an isolated lateral ramus of a right parietal, and NMC 8803, central bar and lateral rami of parietals. Specimens AMNH 5656, NMC 34832 and TMP 1979.11.
caption: G. F. Sternberg preparing a C. belli skull
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