Tricleidus

Tricleidus is an extinct genus of cryptoclidid plesiosaur known from only specimen (BMNH R3539) from the middle Jurassic of United Kingdom. It was first named by Andrews in 1909 and the type species is Tricleidus seeleyi.

One species, T. svalbardensis,Persson, P.O. (1962): Plesiosaurians from Spitsbergen. Norsk Polarinstitutt, Årbok 1961, p. 62-68. Oslo University Press, 169 pp. was moved into Colymbosaurus in 2012. It was found in the Agardhfjellet Formation, Norway.