Genus: Styxosaurus WELLES, 1943
Etymology: Styx, mythological river in Hades, and Greek, sauros, “lizard”; Styx lizard.
= Alzadasaurus WELLES 1943 (partim)
Etymology: In reference to the town of Alzada, Montana, near where the specimen was found, Greek, sauros, “lizard”: Alzada lizard.
= Hydralmosaurus WELLES, 1943
Etymology: Greek, hydralme, “salt water” and Greek, sauros, “lizard”: Salt water lizard.
= Thalassonomosaurus WELLES, 1943
Etymology: Greek, thalassa, “sea”, Greek, nomo, “dwell” and Greek, sauros, “lizard”: Sea-living lizard.
= Woolungosaurus PERSSON, 1960
Etymology: In reference to Woolunga, an Australian aboriginal name for a mythical reptile-like beast, and Greek, sauros, “lizard”: Woolunga lizard.

Species: snowii (WILLISTON, 1890) WELLES, 1943
Etymology:
= Cimoliasaurus snowii WILLISTON, 1890
= Elasmosaurus snowii (WILLISTON, 1890) WILLISTON, 1906

Holotype: KUVP 1301

Locality: Hell Creek, Logan County (was Plum County), Kansas.

Horizon: Niobrara Formation, or Upper Smoky Hill Member.

Biostratigraphy: Spinaptychus sternbergi or Hesperornis zone.

Age: Santonian Stage, or basal Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Triassic.

Material: Skull and 28 cervical vertebrae.

Referred material:

CICIMURII & EVERHART, 2001

Locality: Logan County, Kansas.

Horizon: Sharon Springs Member, Pierre Shale.

Biostratigraphy:

Age: Upper Lower to Lower Middle Campanian Stage, Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous

Material:

NJSM 15435: Nearly complete skeleton lacking skull.
Note: Gastroliths (95) and fragments of Enchodus.

WILLISTON & MOODIE, 1917

= Ogmodirus ischiadicus referred material
WILLISTON 1906
= Styxosaurus snowii WELLES 1943 referred material.

Locality: Plum Creek, Logan County, Western Kansas.

Horizon: Niobrara Formation or Upper Smoky Hill Member.

Biostratigraphy: Spinaptychus sternbergi or Hesperornis zone.

Age: Basal Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material:

YPM 1644 (YPM 636): Scapulae, coracoids, pubes and vertebrae.

_____________________________________________________________________________________

Species: marshii (WILLISTON, 1906) emend OTERO, 2016
= Elasmosaurus marshii WILLISTON, 1906 (nomen dubium)
Etymology: In honor of Othneil Charles Marsh.
= Thalassonomosaurus marshii (WILLISTON, 1906) WELLES, 1943 (nomen dubium)

Note: Otero (2016) placed Thalassonomosaurus marshi in Styxosaurus sp. However, because there is an assigned species name to the specimen, the name should be Styxosaurus marshii not Styxosaurus sp. Holotype: YPM 1645

Locality: Logan County, Kansas.

Horizon: Niobrara Formation or Upper Smoky Hill Member.

Biostratigraphy: Spinaptychus sternbergi or Hesperornis zone.

Age: Basal Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: 14 vertebral centra (cervical, pectoral and dorsal, listed as 32 or 33, but the difference now cannot be accounted for [STORRS, 1999]), numerous spine, centrum and rib fragments, left scapula, and a nearly complete left fore limb, numerous tiny girdle fragments.

Referred material:

YPM 2062: Scapulae.

_____________________________________________________________________________________

Species: pembertoni (WELLES & BUMP, 1949) emend OTERO, 2016
= Alzadasaurus pembertoni WELLES & BUMP, 1949
Etymology:

Note: Otero (2016) placed Alzadasaurus pembertoni in Styxosaurus sp. However, because there is an assigned species name to the specimen, the name should be Styxosaurus pembertoni not Styxosaurus sp.

Holotype: Museum of Geology, South Dakota School of Mines and Technology, No. 451

Locality: 25 miles south of Chamberlain and 11 miles northeast of Iona, Missouri River, Lyman County, South Dakota.

Horizon: Sharon Springs Member, Pierre Shale.

Biostratigraphy:

Age: Upper Lower to Lower Middle Campanian Stage, Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous

Material: Skull and nearly complete skeleton.
Note: Found with 253 quartzite gastroliths.
Note: Paleopathology, humerus shows avascular necrosis (ROTHSCHILDS & STORRS, 2003)

Referred material:

= Alzadasaurus cf. pembertoni NICHOLLS, 1988

Locality: Manitoba Province, Canada.

Horizon: Pembina Member, Pierre Shale.

Biostratigraphy:

Age: Campanian Stage, Upper Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous.

Material:

P83.02.18: Disarticulated specimen.

_____________________________________________________________________________________

Species: kansasensis (WELLES, 1952) emend OTERO, 2016
= Alzadasaurus kansasensis WELLES, 1952
Etymology: In reference to the state of Kansas, where the specimen was found.

Note: Otero (2016) placed Alzadasaurus kansensis in Styxosaurus sp. However, because there is an assigned species name to the specimen, the name should be Styxosaurus kansasensis not Styxosaurus sp.

Holotype: YPM 1130

Locality: Probably along the Smoky Hill River, Logan County, Kansas.
Note: Was thought to be Wallace County, Kansas.

Horizon: Smoky Hill Member, Niobrara Formation.

Biostratigraphy: Hesperornis zone.

Age: Santonian or Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: 28 cervicals, 5 pectorals, 3 dorsals, 5 sacrals, 22 caudal vertebrae, associated spine and other vertebral fragments, rib fragments, the nearly complete right rear limb, 6 isolated phalanges, and most of the pelvis.

Referred material:

= Elasmosaurus ischiadicus WILLISTON, 1906 (Referred specimen.)
= Ogmodirus ischiadicus WILLISTON & MOODIE, 1917 (Referred specimen.)

Pelvis.

_____________________________________________________________________________________

Species: serpentinus (COPE, 1871) emend OTERO, 2016
Etymology:
= Elasmosaurus serpentinus COPE, 1871
= Hydralmosaurus serpentinus (COPE, 1871) WELLES, 1943

Note: Otero (2016) placed Hydralmosaurus serpentinus in Styxosaurus sp. However, because there is an assigned species name to the specimen, the name should be Styxosaurus serpentinus not Styxosaurus sp.

Holotype: AMNH 1495

Locality: A bluff of blue shale in Cedar, Dixon or Dakota County, Nebraska on the southwest side of the Missouri River between Yankton, South Dakota and Sioux City, Iowa.

Horizon: Smoky Hill Member, Niobrara Formation.

Biostratigraphy:

Age: Santonian or Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: 58 cervicals, 3 pectorals, 19 dorsals, 4 sacral, 20 caudal vertebrae, coracoid, humerus, femur, and fragmentary pectoral girdle.

_____________________________________________________________________________________

Species: browni WELLES, 1952
Etymology:

Holotype: AMNH 5835

Locality: Red Bird, Niobrara County, Wyoming.
Note: Note Mule Creek, 15 miles west of Edgemont, South Dakota as reported by WELLES, 1952, as per CARPENTER, 1999.

Horizon: Sharon Springs Member, Pierre Shale.

Biostratigraphy:

Age: Upper Lower to Lower Middle Campanian Stage, Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Skull, 75 vertebrae, pectrum and a pectoral limb.

Referred material:

BROWN, 1904

Locality: Head of Hat Creek Basin, 18 miles, southwest of Edgemont, Fall River County, South Dakota.

Horizon: Sharon Springs Member, Pierre Shale.

Biostratigraphy:

Age: Upper Lower to Lower Middle Campanian Stage, Senonian Subepoch, Upper Gulf Epoch, Late Cretaceous
Note: Now believed to be from the Younger Pierre Shale (MARTIN, SCHUMACHER PARRIS & GRANDSTAFF, 1998)

Material:

AMNH 5803: Fragmentary skeleton with gastroliths.
Note: Pteranodon sp found in the stomach region along with a teleost fish, Scaphites and gastroliths (CICIMURRI & EVERHART, 2001).

_____________________________________________________________________________________

Species: glendowerensis (PERSSON, 1960) SACHS, 2004
= Woolungosaurus glendowerensis PERSSON, 1960
Etymology:

Holotype: QMD 6890 (QM F3567, according to LEES, 1986)

Locality: Glendower Station, near Prairie, Flinders Shire, North Central Queensland State, Australia.

Horizon: Probably Doncaster member, Wallubilla Formation.

Biostratigraphy:

Age: Late Aptian Stage, Middle Gallic Epoch, Upper Early Cretaceous Epoch, Early Cretaceous.

Material: 46 vertebrae (24 cervical including axis, 3 pectoral, 9 doral, 3 sacral, and 7 caudal vertebrae) a number of fragments of neurapophysess and spinous processes, a great number of rib fragments, large parts of scapulae and coracoids, fragments of ilia, ischia and ?pubes, right humerus, nearly complete, both femora, nearly complete, left radius and ulna, 1 tibia or fibula, a number of meso-or metaporial bones, 2 phalanges.

Referred material:

QM 7710: Humerus.

QM F3568: Incomplete left humerus.
Note: SACHS, 2004, No locality data was associated with the specimen, but it most probably belongs to holotype.

 

SACHS, 2004

Locality: Grampian Valley, Richmond Shire, North Queensland State, Australia.

Horizon: Doncaster Member, Wallumbilla Formation.

Biostratigraphy:

Age: Late Aptian Stage, Middle Gallic Epoch, Upper Early Cretaceous Epoch, Early Cretaceous.

Material:

RMF R271: An incomplete skeleton comprising 15 cervical, 3 pectoral, 17 dorsal, and 10 caudal vertebrae, both scapulae, coracoids, clavicles and humeri i manual intermedium, 1 radiale, metacarpals I-III, both ischia, pubes, femora 1 ?fibula, 1 tarsal ?intermedium and 26 phalanges.

 

Locality: Claypan Ridge near Rainscourt Station, Richmond Shire, Queensland Formation, Australia.

Horizon: Doncaster Member, Wallumbilla Formation.

Biostratigraphy:

Age: Late Aptian Stage, Middle Gallic Epoch, Upper Early Cretaceous Epoch, Early Cretaceous.

Material: Anterior portions of both coracoids and 2 dorsal vertebrae.