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The tuatara is the only surviving member of Rhynchocephalia (modernly known as either Sphenodontia or Sphenodontida), an order that has survived virtually unchanged for 200 million years. Tuataras are endemic to New Zealand, and now live only on a small number of offshore islands. It has been classified as an endangered species since 1895. Tuatara, like many native New Zealand animals, are threatened by habitat loss, harvesting, and introduced species such as mustelids and rats.
There are two extant species: Sphenodon punctatus and the much rarer Sphenodon guntheri, or Brothers Island tuatara which is confined to The Brothers Islands in Cook Strait. These have olive skin with yellowish patches.
Though tuataras resemble lizards, the genus has several characteristics unique among reptiles. Its teeth are fused to its jaw bone; it has no external copulatory organs or earholes. Indeed, tuatara were originally classified as lizards in 1831 when the British Museum received a skull. The species remained misclassified until 1867, when Gunther (also at the British Museum) noted certain bird-like, turtle-like, and crocodile-like features and proposed the order Rhynchocephalia for the tuatara and its fossile relatives.
The name tuatara derives from the Māori language, meaning "spiny back". Tuatara feature in a number of indigenous legends. They are held as ariki (God forms). Tuatara are regarded as the messengers of Whiro, the god of death and disaster. Māori women are forbidden to eat tuatara.
Tuatara thrive in much lower temperatures than are tolerated by most reptiles, preferring temperatures of 16–21°C (60–70°F); temperatures over 27°C (80°F) are fatal. Adults are about 50 cm long and weigh between 500 and 1000 grams. Tuatara are notoriously cryptic, and hibernate in winter. Adults are terrestrial and nocturnal, but hatchlings are arboreal and diurnal (likely because the adults are known to eat younger tuatara).
Tuatara are extremely long-lived, with individuals commonly living for over a century. They reproduce very slowly: tuataras take at least ten years to reach sexual maturity, females only lay eggs once every four years, and it takes between 12 and 15 months after copulation for a new tuatara to hatch from its egg. The sex of the hatchling depends on the temperature of the egg, with warmer eggs tending to produce male tuatara, and cooler eggs producing females. Tuatara continue to grow larger for the first thirty-five years of their lives, and they can hold their breath for over an hour.
Like some lizards, the tuatara has a third eye on the top of its head. In adult animals, a scale grows over the eye, and its purpose is unknown. It may be useful in absorbing ultraviolet rays to manufacture vitamin D.
External links
- Animal Diversity Web (http://animaldiversity.ummz.umich.edu/accounts/sphenodon/s._punctatus%24narrative.html)
- Quickfire Facts - New Zealand Native Animals - Tuatara (http://library.christchurch.org.nz/Childrens/FactSheets/Animals/Tuatara.asp)
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