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Temporal range: Late Cretaceous, 95 Ma
Mounted cast of the type specimen, American Museum of Natural History
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Family: Elasmosauridae
Genus: Thalassomedon
Welles, 1943
Species: T. hanningtoni
Welles, 1943
  • Alzadasaurus riggsi Welles, 1943

Thalassomedon is a genus of plesiosaur, named by Welles in 1943. Greek, thalassa, "sea" and Greek, medon, "lord, ruler": Sea lord.


Neck vertebrae

This genus of plesiosaur occurred in North America about 95 mya. It occurs in the Cenomanian strata of the Late Cretaceous rock. Its closest relative is the Elasmosaurus and together they make up the family Elasmosauridae. There are six specimens of varying state of preservation on display at various U.S. museums.



With a length of 12.3 metres (40 ft), the neck comprises 62 vertebrae[1] about 5.9 metres (19 ft) or half the animal. The skull is 47 centimetres (19 in) long, with 5 centimetres (2.0 in) long teeth. The flippers were about 1.5–2 metres (4.9–6.6 ft) long. Stones have been found in its stomach area leading some to theorize that they were used for ballast or digestion. If the latter, stomach action causes the stones to help grind ingested food.

See also[edit]


  1. ^ Carpenter, K. (1999). "Revision of North American elasmosaurs from the Cretaceous western interior." Paludicola, 2(2): 148-173.

External links[edit]