Styxosaurus

Styxosaurus
Temporal range: Late Cretaceous, (100.5-72.1 MYA)
Holotype skull of Styxosaurus snowii
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Superfamily: Plesiosauroidea
Family: Elasmosauridae
Subfamily: Elasmosaurinae
Genus: Styxosaurus
Welles, 1943
Species
  • S. snowii (Williston, 1890; type)
  • S. browni Welles, 1952
  • S. rezaci Smith & O'Keefe, 2023
Synonyms
  • Cimoliasaurus snowii Williston, 1890
  • Elasmosaurus snowii (Williston, 1890)
  • Ogmodirus ischiadicus Williston & Moodie, 1903/1913
  • Thalassonomosaurus marshi (Williston, 1906) Welles, 1943 [originally Elasmosaurus]
  • Alzadasaurus pembertonii Welles & Bump, 1949
  • Alzadasaurus kansasensis Welles, 1952

Styxosaurus is a genus of elasmosaurid plesiosaur that lived during the Late Cretaceous period. Three species are known: S. snowii, S. browni, and S. rezaci. Fossils are known from North America and are mainly found in the Niobrara and Pierre Shale formations. Older fossils are known from the Graneros Shale.