PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Chasmosaurus

Reptilia - Ceratopsidae

Taxonomy

Chasmosaurus was named by Lambe (1914). It is the type genus of Chasmosaurinae.

It was synonymized subjectively with Ceratops by Gregory and Mook (1925).

It was assigned to Monocloniinae by Nopcsa (1928) and Huene (1950); to Ceratopsinae by Tatarinov (1964); to Ceratopinae by Olshevsky and Ford (1994); to Ceratopsidae by Abel (1924), Huene (1927), Hay (1930), Russell (1930), Lull (1933), Parks (1935), Gilmore (1935), Sternberg (1940), Sternberg (1949), Romer (1956), Parsch (1963), Kuhn (1964), Romer (1966), Charig (1967), Swinton (1970), Powell (1973), Molnar (1980), Lehman (1981), Dodson (1983), Russell (1984), Ostrom and Wellnhofer (1986), Clemens (1986), Carroll (1988) and Longrich (2008); and to Chasmosaurinae by Lambe (1915), Lehman (1989), Dodson and Currie (1990), Lehman (1990), Forster and Sereno (1993), Godfrey and Holmes (1995), Lehman (1996), Vickaryous and Ryan (1997), Dodson (1997), Dodson (1997), Eberth et al. (2001), Dodson et al. (2004), Farke (2004), Diem and Archibald (2005), Ryan and Evans (2005), Lucas et al. (2006), Wu et al. (2007), Ryan (2007), Hunt and Lehman (2008), Longrich (2010), Xu et al. (2010), Ryan et al. (2010), Maidment and Barrett (2011), Farke et al. (2011), Farke (2011), Fiorillo and Tykoski (2012), Longrich (2014), Konishi (2015), Evans and Ryan (2015) and Campbell et al. (2016).

Species

C. belli, C. brevirostris, C. kaiseni, C. russelli (syn. Mojoceratops perifania), Monoclonius canadensis

Synonyms

Mojoceratops was named by Longrich (2010).

It was synonymized subjectively with Chasmosaurus by Maidment and Barrett (2011), Konishi (2015) and Campbell et al. (2016).

It was assigned to Chasmosaurinae by Longrich (2010), Farke (2011) and Longrich (2014).
Eoceratops was named by Lambe (1915).

It was considered a nomen dubium by Longrich (2010); it was synonymized subjectively with Chasmosaurus by Lehman (1989), Dodson and Currie (1990), Lehman (1990), Olshevsky and Ford (1994), Dodson et al. (2004) and Campbell et al. (2016).

It was assigned to Eoceratopsinae by Lambe (1915); to Ceratopsinae by Nopcsa (1928) and Huene (1950); to Monocloninae by Tatarinov (1964); and to Ceratopsidae by Joleaud (1922), Abel (1924), Huene (1927), Hay (1930), Russell (1930), Lull (1933), Sternberg (1949), Romer (1956), Parsch (1963), Kuhn (1964), Romer (1966), Charig (1967), Lehman (1981), Dodson (1983), Russell (1984), Ostrom and Wellnhofer (1986), Clemens (1986) and Carroll (1988).
Chasmosaurus kaiseni was named by Brown (1933). Its type specimen is AMNH 5401, a skull, and it is a 3D body fossil. Its type locality is 14 miles below Steveville (30 ft level), which is in a Campanian terrestrial horizon in the Oldman Formation of Canada.

It was synonymized subjectively with Chasmosaurus canadensis by Lehman (1989), Dodson and Currie (1990) and Lehman (1990); it was synonymized subjectively with Chasmosaurus belli by Godfrey and Holmes (1995), Dodson et al. (2004), Currie (2005) and Maidment and Barrett (2011); it was considered a nomen dubium by Longrich (2010) and Campbell et al. (2016).
Protorosaurus was named by Lambe (1914).

It was replaced with Chasmosaurus by Lambe (1914), Hay (1930), Romer (1956), Kuhn (1964), Romer (1966), Dodson and Currie (1990), Dodson et al. (2004) and Campbell et al. (2016).

It was assigned to Ceratopsia by Lambe (1914).
Chasmosaurus brevirostris was named by Lull (1933). Its type specimen is ROM 5436, a partial skull, and it is a 3D body fossil. Its type locality is RTMP Quarry 25, Red Deer River, which is in a Campanian channel sandstone in the Dinosaur Park Formation of Canada.

It was synonymized subjectively with Chasmosaurus belli by Lehman (1989), Dodson and Currie (1990), Godfrey and Holmes (1995), Lehman (1998), Dodson et al. (2004), Ryan and Evans (2005), Currie (2005) and Maidment and Barrett (2011); it was considered a nomen dubium by Campbell et al. (2016).
Monoclonius canadensis was named by Lambe (1902). Its type specimen is NMC 1254, a partial skull, and it is a 3D body fossil. Its type locality is Berry Creek, GSC (NMC 1254), which is in a Campanian/Campanian terrestrial horizon in Canada.

It was recombined as Ceratops canadensis by Hatcher et al. (1907), Brown (1914) and Lambe (1914); it was recombined as Eoceratops canadensis by Lambe (1915), Lambe (1915), Lambe (1916), Gilmore (1923), Parks (1925), Hay (1930), Russell (1930), Lull (1933), Sternberg (1940), Tatarinov (1964), Kuhn (1964), Russell (1964), Charig (1967), Langston (1975) and Lehman (1981); it was recombined as Chasmosaurus canadensis by Lehman (1989), Dodson and Currie (1990), Lehman (1990), Lehman (1993) and Lehman (1996); it was synonymized subjectively with Chasmosaurus belli by Godfrey and Holmes (1995), Dodson et al. (2004), Currie (2005), Maidment and Barrett (2011) and Konishi (2015); it was considered a nomen dubium by Longrich (2010) and Campbell et al. (2016).

Synonymy list

Year	Name and author
1902	Monoclonius canadensis Lambe p. 63 figs. Pl. 17-18
1905	Monoclonius canadensis Lambe p. 3
1907	Ceratops canadensis Hatcher et al. p. 172
1914	Ceratops canadensis Brown p. 378
1914	Protorosaurus Lambe p. 131
1914	Monoclonius canadensis Lambe p. 132
1914	Chasmosaurus Lambe pp. 149-155
1914	Ceratops canadensis Lambe p. 154
1915	Eoceratops Lambe p. 1 figs. Pl. 1-2
1915	Eoceratops canadensis Lambe p. 1
1915	Chasmosaurus Lambe p. 20
1915	Eoceratops Lambe p. 20
1915	Eoceratops canadensis Lambe p. 117
1916	Eoceratops canadensis Lambe p. 194
1922	Eoceratops Joleaud p. 64
1923	Eoceratops canadensis Gilmore p. 51
1924	Chasmosaurus Abel p. 712
1924	Eoceratops Abel p. 712
1925	Eoceratops canadensis Parks p. 5
1927	Ceratops caudensis Huene p. 261
1927	Chasmosaurus Huene p. 261
1927	Eoceratops Huene p. 261
1928	Chasmasaurus Nopcsa p. 185
1928	Eoceratops Nopcsa p. 185
1930	Eoceratops Hay p. 221
1930	Eoceratops canadensis Hay p. 221
1930	Chasmosaurus Hay p. 223
1930	Chasmosaurus Russell p. 149
1930	Eoceratops Russell p. 149
1930	Eoceratops canadensis Russell p. 149
1933	Chasmosaurus kaiseni Brown
1933	Eoceratops Lull p. 91
1933	Eoceratops canadensis Lull p. 91
1933	Chasmosaurus Lull p. 92
1933	Chasmosaurus brevirostris Lull p. 94 figs. Pl. VIIA
1933	Chasmosaurus kaiseni Lull p. 94 fig. 38
1935	Chasmosaurus Gilmore p. 164
1935	Chasmosaurus Parks p. 193
1935	Chasmosaurus brevirostris Parks p. 193
1939	Chasmosaurus kaiseni Riabinin p. 25
1940	Eoceratops canadensis Sternberg p. 471
1940	Chasmosaurus Sternberg p. 478
1940	Chasmosaurus brevirostris Sternberg p. 478
1946	Chasmosaurus kaiseni Gray p. 796
1946	Chasmosaurus brevirostris Gray p. 797
1949	Chasmosaurus brevirostris Lull and Gray p. 493
1949	Chasmosaurus Sternberg p. 41 fig. 1
1949	Eoceratops Sternberg p. 41 fig. 1
1949	Chasmosaurus kaiseni Sternberg p. 42 fig. 1
1950	Chasmosaurus Huene p. 351
1950	Eoceratops Huene p. 351
1956	Chasmosaurus Romer p. 639
1956	Eoceratops Romer p. 639
1963	Chasmosaurus Parsch p. 8
1963	Eoceratops Parsch p. 8
1964	Chasmosaurus Kuhn p. 56
1964	Chasmosaurus brevirostris Kuhn p. 56
1964	Chasmosaurus kaiseni Kuhn p. 56
1964	Eoceratops Kuhn p. 56
1964	Eoceratops canadensis Kuhn p. 56
1964	Chasmosaurus kaiseni Russell p. 13
1964	Eoceratops canadensis Russell p. 13
1964	Eoceratops Tatarinov p. 583
1964	Eoceratops canadensis Tatarinov p. 583
1964	Chasmosaurus Tatarinov p. 585
1966	Chasmosaurus Romer p. 371
1966	Eoceratops Romer p. 371
1966	Chasmosaurus kaiseni Russell p. 21
1966	Chasmosaurus brevirostris Russell p. 30
1967	Chasmosaurus Charig p. 717
1967	Eoceratops Charig p. 717
1967	Eoceratops canadensis Charig p. 717
1970	Chasmosaurus Swinton p. 259
1973	Chasmosaurus Powell p. 118
1975	Eoceratops canadensis Langston p. 1585
1980	Chasmosaurus Molnar p. 138
1981	Eoceratops Lehman p. 209
1981	Eoceratops canadensis Lehman p. 209
1981	Chasmosaurus Lehman p. 214
1981	Chasmosaurus kaiseni Tyson p. 1244
1983	Chasmosaurus Dodson p. 94
1983	Eoceratops Dodson p. 94
1984	Chasmosaurus Russell p. 25
1984	Eoceratops Russell p. 25
1985	Chasmosaurus kaiseni Sloan p. 265
1986	Chasmosaurus Clemens p. 80
1986	Eoceratops Clemens p. 80
1986	Chasmosaurus Ostrom and Wellnhofer p. 116
1986	Eoceratops Ostrom and Wellnhofer p. 116
1986	Chasmosaurus brevirostris Tokaryk p. 195
1988	Chasmosaurus Carroll
1988	Eoceratops Carroll
1989	Chasmosaurus Lehman p. 138
1989	Chasmosaurus canadensis Lehman p. 139
1990	Chasmosaurus Dodson and Currie p. 612
1990	Chasmosaurus canadensis Dodson and Currie p. 612
1990	Chasmosaurus Lehman p. 212
1990	Chasmosaurus canadensis Lehman p. 224
1993	Chasmosaurus Forster and Sereno p. 14
1993	Chasmosaurus canadensis Lehman p. 284
1994	Chasmosaurus Olshevsky and Ford
1995	Chasmosaurus Godfrey and Holmes p. 727
1996	Chasmosaurus Lehman p. 505 fig. 10
1996	Chasmosaurus canadensis Lehman p. 505 fig. 10
1997	Chasmosaurus Dodson p. 12
1997	Chasmosaurus Vickaryous and Ryan p. 492
2001	Chasmosaurus Eberth et al. p. 59
2004	Chasmosaurus Dodson et al. p. 495
2004	Chasmosaurus Farke p. 4
2005	Chasmosaurus Diem and Archibald p. 251
2005	Chasmosaurus Ryan and Evans p. 325
2006	Chasmosaurus Lucas et al. p. 368
2007	Chasmosaurus Ryan p. 391 fig. 12
2007	Chasmosaurus Wu et al. p. 1261 fig. 14
2008	Chasmosaurus Hunt and Lehman p. 1132
2008	Chasmosaurus Longrich p. 994
2010	Chasmosaurus Longrich pp. 682-683
2010	Mojoceratops Longrich p. 682–683 fig. 10
2010	Chasmosaurus Ryan et al. p. 185
2010	Chasmosaurus Xu et al. p. 1634 fig. 3
2011	Chasmosaurus Farke p. 5
2011	Mojoceratops Farke p. 5
2011	Chasmosaurus Farke et al. p. 699
2011	Chasmosaurus Maidment and Barrett p. 4
2012	Chasmosaurus Fiorillo and Tykoski
2014	Chasmosaurus Longrich p. 303 fig. 8
2014	Mojoceratops Longrich p. 303 fig. 8
2015	Chasmosaurus Evans and Ryan
2015	Chasmosaurus Konishi p. 610
2016	Chasmosaurus Campbell et al. p. 34

Is something missing? Join the Paleobiology Database and enter the data

Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia
subclass	Eureptilia	()
—	Romeriida
—	Diapsida	()

Rank	Name	Author
—	Archosauromorpha	(Huene 1946)
—	Crocopoda
—	Archosauriformes	Gauthier 1986
—	Eucrocopoda
—	Archosauria	()
informal	Avemetatarsalia
—	Ornithodira
—	Dinosauromorpha
—	Dinosauriformes
—	Dinosauria	()
—	Ornithischia	()
—	Genasauria
—	Cerapoda
—	Marginocephalia
—	Ceratopsia	()
infraorder	Neoceratopsia
—	Coronosauria
superfamily	Ceratopsoidea
family	Ceratopsidae
subfamily	Chasmosaurinae
genus	Chasmosaurus

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

G. †Chasmosaurus Lambe 1914

show all | hide all

†Chasmosaurus belli Lambe 1902

†Chasmosaurus russelli Sternberg 1940

hide

Invalid names: Mojoceratops perifania Longrich 2010 [synonym]

Invalid names: Chasmosaurus brevirostris Lull 1933 [nomen dubium], Chasmosaurus kaiseni Brown 1933 [nomen dubium], Eoceratops Lambe 1915 [synonym], Mojoceratops Longrich 2010 [synonym], Monoclonius canadensis Lambe 1902 [nomen dubium], Protorosaurus Lambe 1914 [synonym]

Diagnosis

Reference	Diagnosis
N. R. Longrich 2010	Chasmosaurine ceratopsid characterized by the following combination of characters: (1) supraorbital horns reduced (length no more than 200% of basal diameter in adults) or absent; (2) parietal epoccipitals 1 and 2 both upturned and curving forward; (3) parietal caudal rami dorsoventrally compressed and strap-like, with a thickened caudal rim; (4) parietals subequal to squamosals in length, (5) epijugal small, often low and button-like; (6) parietal caudal emargination weakly developed, angle between lateral rami of parietal caudal bar at least 120°, (7) supraorbital horns oriented anterodorsally, (8) frill not erect, long axis of parietal median bar forming an angle of about 30° to the horizontal.
N. R. Longrich 2010 (Mojoceratops)	As for type and only species.
S. C. R. Maidment and P. M. Barrett 2011	Chasmosaurus is diagnosed based on the following combination of characters: (1) Premaxillary flange along entire anterior margin of external naris; (2) supraorbital horns, when present, curve posteriorly along their length; (3) frill broadens posteriorly to form triangular shield with maximum width more than twice the skull width at orbits; (4) medial margin of squamosal, where it articulates with the lateral bar of the parietal, straight; (5) parietal fenestrae large, occupying most of the parietal, and being rounded or anteroposteriorly longer than transversely wide; (6) epiparietals triangular in shape and project posteriorly or dorsally but do not curve anteriorly. Characters 1–3 after Forster et al. (1993). All of these features are seen in other chasmosaurines and do not, therefore, represent autapomorphies, but this combination of features appears to be unique to Chasmosaurus. See discussion for more details.
T. Konishi 2015	From Maidment and Barrett (2011, p. 4): (1) Premaxillary flange along entire anterior margin of external naris; (2) supraorbital horns, when present, curve posteriorly along their length; (3) frill broadens posteriorly to form triangular shield with maximum width more than twice the skull width at orbits; (4) medial margin of squamosal, where it articulates with the lateral bar of the parietal, straight; (5) parietal fenestrae large, occupying most of the parietal, and being rounded or anteroposteriorly longer than transversely wide; (6) epiparietals triangular in shape and project posteriorly or dorsally but do not curve anteriorly. In addition to these, I propose the following new character: (7) squamosal dorsal border laterally adjacent to supratemporal fenestra straight in profile, anteriorly at level with base of postorbital horncore, and sloping posteroventrally at a shallow angle before ascending farther posteriorly to form lateral border of parietal fenestra. Like the other six characters, the last character is not an autapomorphy for Chasmosaurus among chasmosaurines (Maidment and Barrett 2011). The combination of characters 2 and 7 uniquely diagnoses Chasmosaurus, as Agujaceratops Lucas et al., 2006 is the only other chasmosaurine genus to possess character 2, yet in the latter the dorsal squamosal border lateral to the supratemporal fenestra ascends posteriorly instead (Forster et al. 1993, fig. 3). The polarity of character 7 within Chasmosaurinae is presently unknown.
J. A. Campbell et al. 2016	Chasmosaurus is diagnosed based on the following unique combination of characters: (1) Premaxillary flange along entire anterior margin of external naris; (2) postorbital horncores, when present, curve posteriorly along their length; (3) squamosal dorsal border laterally adjacent to dorsal temporal fenestra straight in profile, anteriorly at level with base of postorbital horncore, and sloping posteroventrally at a shallow angle before ascending farther posteriorly to form lateral border of parietal fenestra; (4) medial margin of squamosal, where it articulates with the lateral bar of the parietal, straight; (5) frill broadens posteriorly to form rectangular to triangular shield with maximum width more than twice the skull width at orbits; (6) parietal fenestrae large, occupying most of the parietal, and being rounded or anteroposteriorly longer than transversely wide; and (7) epiparietals straight and triangular in shape and oriented posteriorly or anterodorsally.