This is thought to be the first case of tuatara successfully breeding in the wild on New Zealand's North Island in over 200 years. Description Tuatara are the largest reptile in New Zealand. Adult S. punctatus males measure in length and females . Tuatara are sexually dimorphic, males being larger. The San Diego Zoo even cites a length of up to . Males weigh up to , and females up to . Brother's Island tuatara are slightly smaller, weighing up to 660 g (1.3 lb). Their lungs have a single chamber with no bronchi. The tuatara's greenish brown colour matches its environment, and can change over its lifetime. Tuatara shed their skin at least once per year as adults, and three or four times a year as juveniles. Tuatara sexes differ in more than size. The spiny crest on a tuatara's back, made of triangular, soft folds of skin, is larger in males, and can be stiffened for display. The male abdomen is narrower than the female's. Skull The ancestor of diapsids had a skull with two openings in the temporal region – upper and lower temporal fenestra on each side of the skull bounded by complete arches. The upper jaw is firmly attached to the posterior of skull. This makes for a very rigid, inflexible construction. The skull of the tuatara has a similar structure, with both upper and lower temporal openings. However, the lower temporal bar (sometimes called the cheek bone) is incomplete in some fossil Rhynchocephalia, suggesting its presence in the tuatara is a distinctive (autapomorphic) feature rather than one inherited from a common ancestor. The tip of the upper jaw is beak-like and separated from the remainder of the jaw by a notch. There is a single row of teeth in the lower jaw and a double row in the upper, with the bottom row fitting perfectly between the two upper rows when the mouth is closed. This specific tooth arrangement is not seen in any other reptile; although most snakes have a double row of teeth in their upper jaws, their arrangement and function is different from the tuatara's. The structure of the jaw joint allows the lower jaw to slide forwards after it has closed between the two upper rows of teeth. This mechanism allows the jaws to shear through chitin and bone. Fossils indicate that the jaw mechanism began evolving at least 200