Cryptoclidus (crip-TOE-clide-us) was a marine reptile of the plesiosaur family from the Middle Jurassic Period in England.

It is estimated to have weighed about 8 tons and to have been about 8 metres long. Despite looking clumsy and cumbersome, in water it would have become a thing of grace, using all four limbs as paddles, to swim and to hunt the shoals of fish and squid-like creatures. Evidence for this reptile is relatively poor.

Like many prehistoric creatures, it was made famous by the BBC's Walking with Dinosaurs.

Sauropterygia