Diphydontosaurus was a sphenodontian reptile from the Late Triassic of England and Italy. This small animal was related to the living tuatara (Sphenodon). Diphydontosaurus may have hunted and eaten insects in the crevices of ancient caves using its claws. It may have grown to a length of 4 inches (10 cm). It is a rhynchocephalian more derived than Gephyrosaurus, yet more primitive than Planocephalosaurus, and shares traits with both of them.