PBDB Taxon

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

Styxosaurus

Reptilia - Plesiosauria - Elasmosauridae

Taxonomy

Styxosaurus was named by Welles (1943) [Sepkoski's age data: K Sn]. Its type is Styxosaurus snowii.

It was assigned to Alzadasaurinae by Welles (1962); to Plesiosauria by Sepkoski (2002); to Elasmosauridae by Welles (1943), Welles (1949), Carroll (1988), Carpenter (1999), O'Keefe (2001), Ketchum and Benson (2010) and Otero et al. (2012); to Styxosaurinae by Otero (2016); and to Elasmosaurinae by O'Gorman (2019).

Species

Hydralmosaurus serpentinus, S. browni, S. snowii (syn. Alzadasaurus pembertoni) (type species), Thalassonomosaurus marshii

Synonyms

Elasmosaurus marshii was named by Williston (1906). Its type specimen is YPM 1645, a partial skeleton (scapula, 32 vertebrae, and nearly complete forelimb), and it is a 3D body fossil. Its type locality is Elasmosaurus marshii type locality, Logan County, which is in a Coniacian/Santonian marine chalk in the Niobrara Formation of Kansas.

It was recombined as Thalassonomosaurus marshii by Welles (1943); it was recombined as Thalassonomosaurus marshi by Welles (1943); it was considered a nomen vanum by Welles (1962); it was considered a nomen dubium by Storrs (1999); it was synonymized subjectively with Styxosaurus snowii by Carpenter (1999).
Hydralmosaurus was named by Welles (1943) [Sepkoski's age data: K u].

It was synonymized subjectively with Styxosaurus by Otero (2016).

It was assigned to Alzadasaurinae by Welles (1962); to Elasmosauridae by Welles (1943), Welles (1949), Carroll (1988), Storrs (1999) and Carpenter (1999); and to Plesiosauria by Sepkoski (2002).

Synonymy list

Year	Name and author
1906	Elasmosaurus marshii Williston pp. 229-231 fig. 4
1943	Hydralmosaurus Welles
1943	Styxosaurus Welles
1943	Thalassonomosaurus marshi Welles
1943	Thalassonomosaurus marshii Welles
1943	Hydralmosaurus Welles pp. 185-186 fig. 29
1943	Styxosaurus Welles p. 188 fig. 31
1949	Hydralmosaurus Welles
1949	Styxosaurus Welles
1962	Hydralmosaurus Welles p. 4
1962	Styxosaurus Welles p. 4
1988	Hydralmosaurus Carroll
1988	Styxosaurus Carroll
1999	Styxosaurus Carpenter p. 158 fig. 15
1999	Hydralmosaurus Carpenter p. 168 fig. 15
1999	Hydralmosaurus Storrs p. 5
2001	Styxosaurus O'Keefe p. 19 fig. 20
2002	Hydralmosaurus Sepkoski
2002	Styxosaurus Sepkoski
2010	Styxosaurus Ketchum and Benson p. 15 fig. 6
2012	Styxosaurus Otero et al.
2016	Styxosaurus Otero
2019	Styxosaurus O'Gorman

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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
subclass	Amphibiosauria	Kuhn 1967

Rank	Name	Author
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia
subclass	Eureptilia	()
—	Romeriida
—	Diapsida	()
suborder	Sauropterygia
order	Plesiosauria	de Blainville 1835
superfamily	Plesiosauroidea	Welles 1943
family	Elasmosauridae	Cope 1869
—	Euelasmosaurida
—	Elasmosaurinae
genus	Styxosaurus

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. †Styxosaurus Welles 1943

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†Styxosaurus browni Welles 1952

†Styxosaurus snowii Williston 1890

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Invalid names: Alzadasaurus pembertoni Welles and Bump 1949 [synonym]

Invalid names: Hydralmosaurus Welles 1943 [synonym], Thalassonomosaurus marshii Williston 1906 [nomen dubium]

Diagnosis

No diagnoses are available

Measurements

No measurements are available

Composition:

hydroxyapatiteo

Environment:

marineo

Locomotion:

actively mobileo

Life habit:

aquatico

Depth habitat:

surfaceo

Diet:

carnivoreo

Reproduction:

viviparouso

Created:

2009-07-20 06:05:48

Modified:

2011-08-12 01:58:15

Source: o = order

Reference: Kiessling 2004

Age range: base of the Santonian to the top of the Middle Campanian or 86.30000 to 70.60000 Ma

Collections (8 total)

Time interval	Ma	Country or state	Original ID and collection number
Late/Upper Coniacian - Santonian	89.3 - 83.6	USA (Kansas)	Elasmosaurus marshii (117842)
Santonian	86.3 - 83.6	USA (Kansas)	Cimoliasaurus snowii (116624) Elasmosaurus snowii (117841)
Early/Lower Campanian	83.5 - 70.6	USA (South Dakota)	S. browni (35333)
Early/Lower Campanian	83.5 - 70.6	USA (Wyoming)	S. browni (77348)
Early/Lower Campanian - Middle Campanian	83.5 - 70.6	USA (South Dakota)	Alzadasaurus pembertoni (102092)
Early/Lower Campanian - Middle Campanian	83.5 - 70.6	USA (Nebraska)	Hydralmosaurus serpentinus (116621)
Middle Campanian	83.5 - 70.6	USA (Kansas)	S. snowii (25692)