Testudines, Squamata, and Crocodilia are three of four orders of reptiles. The fourth order is Sphenodontia of which the Tuatara is the only living member. It is endemic to New Zealand and resembles a lizard more so than the other orders. Tuatara pre-date dinosaurs and have features that are not only ancient but are unique among animals and little understood. For example, they have what is commonly called a third eye and can hear even though they have no external ears. Their is skeleton is remarkable as it resembles features found in fish. They also have have two rows of upper teeth that overlap one bottom row of teeth.