The Tuatara is a species of reptile endemic to New Zealand and its surrounding islands, belonging to the genus Sphenodon. Their name derives from the Māori language, and means "peaks on the back" referencing their unique spiny vertebral crests. Although resembling most lizards, they are part of a unique lineage of reptiles, the order Rhynchocephalia, which originated in the Triassic period around 250 million years ago and flourished throughout the Mesozoic until being near completely wiped out by the KPG mass extinction event some 66 million years ago. Tuatara are typically a mix of green, brown, and gray in color, measure upwards 31 inches in length and upwards of 3lbs in weight. They sport a spiny white crest along the back, two rows of teeth in the upper jaw overlapping one row on the lower jaw, and are able to hear remarkably well despite lacking an external ear. They are also unusual in having a pronounced photoreceptive third eye, which is thought to be involved in sensing circadian and seasonal cycles. Tuataras thrive in temperatures much lower than those tolerated by most reptiles, and hibernate during winter. Their diet consists of insects, arachnids, crustaceans, other arthropods, frogs, lizards, and bird eggs. While juveniles are diurnal, adults are typically nocturnal or crepuscular depending on the season, spending the day inside of shallow burrows which they may share with seabirds such as petrels, prions, and shearwaters. Tuatara probably have the slowest growth rates of any reptile taking 10 to 20 years to reach sexual maturity, and up to 35 years to reach full size. Mating occurs in midsummer typically once every four years. Mothers lay 2 to 19 white, soft-shelled eggs in nesting burrows, which are covered and incubated for 12 to 15 months before hatching. Barring tortoises, tuataras have the longest lifespan of any reptile with individuals regularly living well past 100 years.
