Hydrotherosaurus Welles, 1943
The type skeleton of Hydrotherosaurus was discovered in the Panoche Hills by Mr. Frank C. Paiva in 1937, and excavated by the University of California Museum of Palaeontology, Berkeley, and Fresno State College.The taxon was described in detail by Samuel P. Welles (1943, 1952), and differs most obviously from other elasmosaurids in that it possesses 60 cervical vertebrae. Hydrotherosaurus is known from one of the most complete elasmosaurid skeletons discovered to date and is therefore one of the best known members of this family. A cast of the holotype skeleton is on public display in the California Academy of Sciences.
Welles (1943) derives the genus from the word "fisherman", hence "fisherman lizard". However, the genus translates more literally as "water beast reptile".
H. alexandrae Welles, 1943
The species name honours Miss Annie M. Alexander, "who has contributed so much to the work on the vertebrates of the West" (Welles, 1943, p. 126).
Type specimen: U. C. Mus. Pal. no 33912. A nearly complete skeleton.
Referred material: none
Age and Location
Moreno Formation (Maastrichtian), Late Cretaceous. Discovered in the Sun Ray gypsum mine in the Panoche hills, south of Moreno Gulch, near Mendota, Freso County, California, USA.