Cryptoclidus

Cryptoclidus, often wrongly spelled ‘Cryptocleidus’ after Andrews (1909), is a moderately sized plesiosaur up to 3 metres long. It is known from a large number of individual specimens from the Oxford Clay Formation. Fossils of Cryptoclidus are relatively common, and provide a complete ontogenetic sequence from very young to old adult individuals. This makes Cryptoclidus one of the most studied and best understood of all plesiosaurs.

Full mounted skeletons of Cryptoclidus can be seen in several major museums including the Musee Palaeontologique, Paris; the Natural History Museum, London; the Hunterian Museum, Glasgow; and the American Museum of Natural History, New York.

The genus has diagnostic teeth with reduced ornamentation. Each premaxilla contains six teeth. Cryptoclidus lacks suborbital fenestrae on its palate and has a large anterior interpterygoid vacuity. A small foramen is located along the postorbital-squamosal junction in C. eurymerus.

Cryptoclidus used its numerous sharp teeth to catch squid and fish, or perhaps to sift silty sediments for benthic animals such as crustaceans.

C. richardsoni differs from C. eurymerus only in the form of its humerus, which is more expanded distally. The genus and species ‘Apractocleidus teretipes‘ was introduced by Smellie (1916) for a specimen now regarded as an old-adult specimen of Cryptoclidus.