There are many noticeable distinguishing morphological differences between lizards, tuataras, and snakes. The remaining snake species, tuataras, and amphisbaenians, are carnivores. Near the entrance is an enclosure for tuataras. Snakes, tuataras and many lizards lack osteoderms. Squamates are a monophyletic group included, with the Sphenodontia (e.g. tuataras), in the Lepidosauria. They are thought to have fed on large invertebrates, lizards, tuataras and even small birds. Reptiles are a class of animals comprising turtles, tuataras, lizards, snakes and crocodiles. There are, however, other animals that have acrodont dentition such as tuataras.. The parietal foramen (a hole which holds the "third eye" in modern tuataras) is teardrop-shaped. The only living sub-group is the Lepidosauria&colon; extant lizards, snakes and tuataras. Tuataras must use their cloacae for reproduction. Recent paleogenetic discoveries show that tuataras are prone to quick speciation. A tuatara fence has also been built to stop tuataras from getting through. Tuataras also have the ability to autotomize their tails. Tuataras superficially resemble lizards but the lineages diverged in the Triassic period.