Overview
The Tuatara (Sphenodon punctatus) is a biological treasure and one of Earth’s most famous ‘living fossils,’ the sole surviving representative of Rhynchocephalia—an ancient reptilian order that flourished alongside the early dinosaurs over 200 million years ago. Endemic strictly to New Zealand, this extraordinary creature is not a true lizard, but a distinct evolutionary lineage that has preserved archaic skeletal structures long lost in all other modern reptiles. Surviving across predator-free offshore islands, the tuatara offers an irreplaceable evolutionary window into the dawn of terrestrial vertebrate life.
Biology and Physical Characteristics
The physical anatomy of Sphenodon punctatus exhibits remarkable primitive specializations. Along its back runs a spiny crest of soft, triangular skin spines (giving it its Māori name, meaning ‘peaks on the back’). Most astonishingly, hatchling tuataras possess a well-developed ‘parietal eye’ (third eye) complete with its own lens, retina, and nerve connection to the brain; while overgrown by scales in adults, this photoreceptive organ plays a crucial role in setting circadian rhythms and hormonal thermoregulation. Their jaw features a unique double row of upper teeth that overlap a single lower row, shearing prey with a forward sawing motion unmatched in the animal kingdom.
Behavior and Ecology
Tuataras are nocturnal, cold-adapted reptiles capable of thriving at body temperatures as low as 41°F (5°C)—conditions that would completely paralyze typical squamates. They maintain a mutualistic relationship with burrowing seabirds, such as petrels and shearwaters, frequently cohabiting in petrel burrows. The seabirds bring guano that fertilizes the soil and attracts a wealth of invertebrate prey, including giant wētā, beetles, and spiders, which form the cornerstone of the tuatara’s diet. Their metabolism is exceptionally slow, resulting in century-long lifespans and reproductive maturity taking up to two decades.
Conservation and Human Impact
Once widespread across mainland New Zealand, tuataras were completely wiped out on the mainland following the introduction of Polynesian rats (kiore) and European ship rats, surviving only on roughly 32 rodent-free offshore islands. Following intensive conservation campaigns spearheaded by the New Zealand Department of Conservation (DOC)—including total rodent eradication on key islands and captive incubation programs—tuatara populations have rebounded to over 50,000 individuals. Successful reintroductions into predator-fenced mainland sanctuaries like Zealandia in Wellington have marked a triumphant return to their ancestral home.
Interesting Factoid
The tuatara has a functional third eye on top of its head, complete with a lens, cornea, and retina, which can be clearly seen in young hatchlings before becoming covered by opaque scales.
Last updated: October 2026