Genus: Styxosaurus WELLES, 1943
Etymology: Styx, mythological river in Hades, and Greek, sauros, “lizard”; Styx lizard.

Species: snowii (WILLISTON, 1890) WELLES, 1943

Referred material:

= Alzadasaurus pembertoni WELLES & BUMP, 1949

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.


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

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