[2] Cryptoclidus was a plesiosaur whose specimens include adult and juvenile skeletons, and remains which have been found in various degrees of preservation in England, Northern France, Russia, and South America.

[6] In 2016, there was a report about a fragmentary Cryptoclidus postcranial skeleton from the Callovian deposits of Nikitino village in Spassky District, Ryazan Oblast, Russia,[7] but later Zverkov et al. defined it as an intedermitate cryptoclidid.

[1][9] The fragile build of the head and teeth preclude any grappling with prey, and suggest a diet of small, soft-bodied animals such as squid and shoaling fish.

Cryptoclidus may have used its long, intermeshing teeth to strain small prey from the water, or perhaps sift through sediment for buried animals.

[10] The size and shape of the nares and nasal openings have led Brown and Cruickshank (1994) to argue that they were used to sample seawater for smells and chemical traces.