PBDB Taxon

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Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Champsosaurus

Reptilia

Taxonomy

Champsosaurus was named by Cope (1876). It is not extant. Its type is Champsosaurus profundus. It is the type genus of Champsosauridae.

It was assigned to Rhynchocephalia by Baur (1887); to Choristodera by Cope (1876), Brown (1905) and Russell (1956); to Champsosauridae by Hay (1902), Hay (1930), Estes (1964), Estes and Berberian (1970), Erickson (1972), Estes (1976), Erickson (1981), Carroll (1988), Evans (1990), Evans (1991), Cvancara and Hoganson (1993), Gao and Fox (1998), Peng et al. (2001) and Gao and Fox (2005); and to Neochoristodera by Matsumoto et al. (2007), Matsumoto and Evans (2010), Matsumoto et al. (2013) and Matsumoto et al. (2019).

Species

C. albertensis, C. ambulator, C. annectens, C. australis, C. brevicollis, C. gigas, C. inelegans, C. inflatus, C. laramiensis, C. lindoei, C. natator, C. norelli, C. profundus (type species), C. puercensis, C. saponensis, C. tenuis, C. vaccinsulensis

Synonyms

Champsosaurus puercensis was named by Cope (1882). Its type specimen is AMNH 1100, a set of vertebrae, and it is a 3D body fossil.

It was synonymized subjectively with Champsosaurus laramiensis by Erickson (1972); it was considered a nomen dubium by Sullivan and Lucas (1986); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus saponensis was named by Cope (1882). Its type specimen is AMNH 1627, a set of vertebrae, and it is a 3D body fossil.

It was synonymized subjectively with Champsosaurus laramiensis by Erickson (1972); it was considered a nomen dubium by Sullivan and Lucas (1986); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus inflatus was named by Parks (1933).

It was synonymized subjectively with Champsosaurus natator by Erickson (1972); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus inelegans was named by Parks (1933).

It was synonymized subjectively with Champsosaurus natator by Erickson (1972); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus australis was named by Cope (1881). Its type specimen is AMNH 1626, a set of vertebrae, and it is a 3D body fossil.

It was synonymized subjectively with Champsosaurus laramiensis by Erickson (1972); it was considered a nomen dubium by Sullivan and Lucas (1986); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus profundus was named by Cope (1876). It is not extant. It is the type species of Champsosaurus.

It was synonymized subjectively with Champsosaurus natator by Erickson (1972); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus annectens was named by Cope (1876). It is not extant.

It was synonymized subjectively with Champsosaurus natator by Erickson (1972); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus brevicollis was named by Cope (1876). It is not extant.

It was synonymized subjectively with Champsosaurus natator by Erickson (1972); it was considered a nomen vanum by Gao and Fox (1998).
Champsosaurus vaccinsulensis was named by Cope (1876).

It was recombined as Plesiosaurus vaccinsulensis by Hay (1930); it was considered a nomen vanum by Welles (1962), Erickson (1972) and Gao and Fox (1998).

Synonymy list

Year	Name and author
1876	Champsosaurus Cope pp. 348-350
1876	Champsosaurus profundus Cope pp. 350-351
1876	Champsosaurus annectens Cope pp. 351-352
1876	Champsosaurus brevicollis Cope pp. 352-353
1876	Champsosaurus vaccinsulensis Cope p. 353
1881	Champsosaurus australis Cope
1882	Champsosaurus saponensis Cope
1882	Champsosaurus puercensis Cope p. 195
1882	Champsosaurus saponensis Cope p. 196
1887	Champsosaurus Baur p. 100
1902	Champsosaurus Hay p. 460
1902	Champsosaurus annectens Hay p. 460
1902	Champsosaurus australis Hay p. 461
1902	Champsosaurus brevicollis Hay p. 461
1902	Champsosaurus profundus Hay p. 461
1902	Champsosaurus puercensis Hay p. 461
1902	Champsosaurus saponensis Hay p. 461
1902	Champsosaurus vaccinsulensis Hay p. 461
1902	Champsosaurus annectens Lambe p. 45
1905	Champsosaurus Brown
1930	Plesiosaurus vaccinsulensis Hay p. 116
1930	Champsosaurus Hay p. 132
1930	Champsosaurus annectens Hay p. 133
1930	Champsosaurus australis Hay p. 133
1930	Champsosaurus brevicollis Hay p. 133
1930	Champsosaurus profundus Hay p. 133
1930	Champsosaurus puercensis Hay p. 133
1930	Champsosaurus saponensis Hay p. 133
1933	Champsosaurus inflatus Parks p. 131
1933	Champsosaurus inelegans Parks p. 135
1956	Champsosaurus Russell p. 4
1964	Champsosaurus Estes p. 99
1970	Champsosaurus Estes and Berberian p. 4
1972	Champsosaurus Erickson p. 8
1976	Champsosaurus Estes p. 507
1981	Champsosaurus Erickson
1988	Champsosaurus Carroll
1990	Champsosaurus Evans
1991	Champsosaurus Evans
1993	Champsosaurus Cvancara and Hoganson p. 15
1993	Champsosaurus profundus Cvancara and Hoganson p. 15
1998	Champsosaurus Gao and Fox p. 315
2001	Champsosaurus Peng et al. p. 32
2005	Champsosaurus Gao and Fox p. 439
2007	Champsosaurus Matsumoto et al. p. 342
2010	Champsosaurus Matsumoto and Evans
2013	Champsosaurus Matsumoto et al.
2019	Champsosaurus Matsumoto et al.

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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

Rank	Name	Author
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia
subclass	Eureptilia	()
—	Romeriida
—	Diapsida	()
—	Eosuchia	()
—	Neodiapsida
—	Sauria	Gauthier 1984
—	Choristodera	()
suborder	Neochoristodera	Evans and Hecht 1993
genus	Champsosaurus

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. †Champsosaurus Cope 1876

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†Champsosaurus albertensis Parks 1927

†Champsosaurus ambulator Brown 1905

†Champsosaurus gigas Erickson 1972

†Champsosaurus laramiensis Brown 1905

†Champsosaurus lindoei Gao and Fox 1998

†Champsosaurus natator Parks 1933

†Champsosaurus norelli Brownstein 2022

†Champsosaurus tenuis Erickson 1981

Invalid names: Champsosaurus annectens Cope 1876 [nomen vanum], Champsosaurus australis Cope 1881 [nomen vanum], Champsosaurus brevicollis Cope 1876 [nomen vanum], Champsosaurus inelegans Parks 1933 [nomen vanum], Champsosaurus inflatus Parks 1933 [nomen vanum], Champsosaurus profundus Cope 1876 [nomen vanum], Champsosaurus puercensis Cope 1882 [nomen vanum], Champsosaurus saponensis Cope 1882 [nomen vanum], Champsosaurus vaccinsulensis Cope 1876 [nomen vanum]

Diagnosis

Reference	Diagnosis
K. -Q. Gao and R. C. Fox 1998	Champsosaurus can be diagnosed by a suite of derived character states as follows: great elongation of snouth, exceeding 1/2 of skull length; interorbital width narrower than diameter of orbit; lacrimal strongly reduced to small triangle; postorbital excluded from formation of orbit; premaxilla/vomer contact lost; internarial present; choanae in posterior portion, in correspondence with elongation of vomer; interpterygoid foramen small, enclosed both anteriorly and posteriorly by pterygoids and located near posterior border of suborbital fenestra; suborbital fenestra shortened and kidney-shaped pterygoid/parasphenoid articulation fused; craniomandibular joint anterior to level of occipital condyle; neomorph forming most of ventral border of posttemporal fenestra; paraoccipital process strongly deflected ventrally; basal tubera of basisphenoid expanded posteroventrally and wing-like; elongation of mandibular symphysis to over 1/2 of length of tooth row; splenial strongly intervening in mandibular symphysis.