Cryptosaurus (meaning 'hidden lizard') is a dubious genus of dinosaur known from a partial femur from the Late Jurassic of England. The femur was found by the geologist Lucas Ewbank and donated by him to the Woodwardian Museum at Cambridge in 1869. Cryptosaurus was the same year named by British paleontologist Harry Seeley; the type species is Cryptosaurus eumerus. The genus name is derived from Greek kryptos, 'hidden', a reference to he rarity of the find. The specific name name means 'well-formed thigh' in Greek, a reference to the stout build of the bone.
Contributions by Firsfron, J. Spencer, and MWAK.