The tuatara (Sphenodon punctatus) is the last surviving member of the rhynchocephalus reptiles. It was featured in the fifth episode of Walking with Dinosaurs, set around 102 MYA.
Externally, the tuatara resembles its distant cousins the lizards. It has a massive body, up to 76 cm long, colored olive-green, weighing up to 0.5 kg (females) and 1 kg (males).
It has a short ridge made from triangular scales along its back and tail.
The tuatara - as shown in the WWD - lives in burrows, where it spends most of the day (it's nocturnal). In modern times, storm petrels (birds) may co-habit with this reptile, even though it occasionally eats their chicks.
Sexual maturity of the tuatara occurs at about 20 yrs. (They can live up to 50 yrs in captivity). The female lays 8-15 hard-shelled eggs. After 12–15 months the newborns hatch, completely independent.
Currently, the tuatara is an endangered species.