Cryptosaurus was for a long time known as Cryptodraco, which is an unnecessary replacement name. In 1889, Richard Lydekker renamed Cryptosaurus as he believed the name Cryptosaurus was already previously in use for another animal (Cystosaurus Geoffroy, described in 1832). This was in error, a mistake originally caused by a wrong spelling of Cystosaurus in the French Bibliothèque universelle des sciences, belles-lettres, et arts, and the name Cryptosaurus has precedence.