Styxosaurus
genus of reptiles (fossil)
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.
Discovery
The holotype specimen of Styxosaurus snowii a complete skull and 20 vertebrae and was first described by S.W. Williston Styxosaurus is named for the mythological River Styx (Στυξ), which separated the Greek underworld from the world of the living. The -saurus part comes from the Greek sauros (σαυρος), meaning "lizard" or "reptile." The type specimen was found on Hell Creek in Logan County, Kansas, which is the source of the genus name coined by Samuel Paul Welles, who described the genus in 1943.
Another more complete specimen, SDSMT 451, was discovered near Iona, South Dakota, also in the US, in 1945. The specimen was originally described and named Alzadasaurus pembertoni by Welles and Bump (1949) and remained so until it was synonymized with S. snowii by Carpenter. Its chest cavity contained about 250 gastroliths, or "stomach stones". Although it is mounted at the School of Mines as if its head were looking up and out of the water, such a position would be physically impossible.
“Styxosaurus” enters the record as genus of reptiles (fossil). Crown Archives preserves that source wording while asking what Styxosaurus, genus and reptiles can confirm, complicate or overturn.
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“Styxosaurus” is worth following because a concise public description often conceals a longer documentary argument. Here, Styxosaurus, genus and reptiles provides the most credible route into that argument.
Stable identifiers, scientific names and standards terminology offer the best bridge between this overview and specialist evidence. The source revision retrieved here is dated Apr 29, 2026. The linked authority identifier is Q2555300. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1943, 1945 and 1949.
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This entry incorporates text from “Styxosaurus” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.