New Zealand drifted apart from the other continents before lizards and mammals evolved. It has no native mammals or lizards. Any species of these found on the islands are non-native and may have arrived by hitchhiking on human cargo or by deliberate introduction by humans.
The tuatara found on the islands are not lizards, even though they look superficially like lizards, as they are classified in the reptilian order Rhynchocephalia and family Sphenodontidae. Tuatara are different from lizards in lacking a penis. Snakes and lizards have a pair of hemipenes, and they are classified in the order Squamata. Nevertheless, the tuatara is the closest living relative of lizards and snakes. The tuatara and lizards and snakes are classified as lepidosaurs. Dinosaurs, crocodilians and the ancestor of birds are classified in the Archosauria. Lizards, snakes, tuatara, crocodilians, dinosaurs, and the ancestors of birds are all diapsid reptiles, with 2 temporal opening in the skull. In contrast, the reptilian ancestors of mammals have a singe temporal opening, and they are classified as synapsid reptiles.