Stratum.black
Elasmosaurus — Elasmosaurus
Elasmosaurus — DiBgd, Wikimedia Commons, CC BY SA 4.0

Marine reptile

Elasmosaurus

Elasmosaur

Elasmosaurus platyurus is the long-necked plesiosaur of the Pierre Shale of Kansas, with 72 neck vertebrae, named by Cope in 1868 and famously reconstructed with the head on the tail. Elasmosaurid vertebrae, paddle bones and striated teeth from the Pierre Shale and Niobrara are sold to genus with caution; gastroliths from plesiosaur skeletons are also collected.

PhylumChordata
ClassReptilia
OrderPlesiosauria
FamilyElasmosauridae
GroupMarine reptile
Rank (PBDB)genus· Paleobiology Database
AuthorCope 1868· Paleobiology Database
Classification (PBDB)Chordata › Reptilia › Plesiosauria › Elasmosauridae· Paleobiology Database
Range (PBDB)93.9–72.2 Ma· Paleobiology Database
PBDB occurrences9· Paleobiology Database

Photographs

Elasmosaurus — Elasmosaurus serpentinus Cope, 1877
Elasmosaurus serpentinus Cope, 1877 — Smithsonian Institution (NMNHPALEO), Smithsonian Open Access, CC0
Elasmosaurus — Elasmosaurus (NHMUK PV R 1300 b)
Elasmosaurus (NHMUK PV R 1300 b) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Age

Formations

Elsewhere

Cite this article

Stratum Study. "Elasmosaurus" (Taxon). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/taxa/elasmosaurus. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-elasmosaurus,
  title        = {Elasmosaurus},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/taxa/elasmosaurus}},
  year         = {2026},
  note         = {Taxon article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, pbdb, wikidata, commons, smithsonian, nhm. Accessed 2026-09-20.}
}

Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.