Rhynchocephalia

Rhynchocephalia is an order of reptiles that, together with squamates (lizards and snakes), forms the group Lepidosauria. Fossil records show rhynchocephalians first appearing in the Triassic, and they were once diverse and widespread. Today the order is represented by a single living lineage, the tuataras, which survive only in New Zealand and its surrounding islands. The two living species, Sphenodon punctatus (the common tuatara) and Sphenodon guntheri (Hector’s tuatara), belong to the family Sphenodontidae and retain several primitive traits not found in most other reptiles.

Anatomically, tuataras possess several features that distinguish them from lizards and other reptiles. They have a diapsid skull, a well-developed parietal or pineal eye, and acrodont dentition, with teeth fused to the jaw and arranged in a single row on each jaw. They also have a robust body, well-developed sensory organs, and external ear openings.

Tuataras are native to New Zealand and its offshore islands, where they occupy coastal to forested habitats and typically shelter in burrows or rocky crevices. They tend to be slow-moving and have a long lifespan, with relatively late sexual maturity compared with many other reptiles. Their diet consists of insects, other invertebrates, and small vertebrates.

Reproduction is oviparous, with eggs laid in burrows. Incubation is lengthy, and growth to maturity is slow, contributing to their vulnerability to rapid environmental change. Rhynchocephalia faces significant conservation challenges, principally from introduced predators and habitat loss on the islands where tuataras live. Conservation programs focus on predator control and the maintenance of predator-free habitats.