A rare reptile with lineage dating back to the dinosaur age has been found nesting on the New Zealand mainland for the first time in about 200 years.

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Four leathery white eggs from an indigenous tuatara were found by staff at the Karori Wildlife Sanctuary in the capital Wellington, during routine maintenance work, conservation manager Rouen Epson said.

"The nest was uncovered by accident and is the first concrete proof we have that our tuatara are breeding," Ms Epson said. "It suggests that there may be other nests in the sanctuary we don't know of."

Tuatara, dragon-like reptiles that grow to up to 32ins, are the last descendants of a species that walked the earth with the dinosaurs 225 million years ago, zoologists say.

They have unique characteristics, such as two rows of top teeth closing over one row at the bottom. They also have a pronounced parietal eye, a light-sensitive pineal gland on the top of the skull. This white patch of skin - called its "third eye" - slowly disappears as they mature.

A native species to New Zealand, tuatara were nearly extinct on the country's three main islands by the late 1700s due to the introduction of predators such as rats. They still live in the wild on 32 small offshore islands cleared of predators.

A population of 70 tuatara was established at the Karori Sanctuary in 2005. Another 130 were released in the sanctuary in 2007.

The sanctuary, a 620-acre wilderness minutes from central Wellington, was established to breed native birds, insects and other creatures securely behind a predator-proof fence.

Ms Empson said that the four eggs - the size of ping-pong balls - were unearthed today but that there were probably more because the average nest contains around 10 eggs.

The eggs were immediately covered up again to avoid disturbing incubation.

If all goes well, juvenile tuatara could hatch any time between now and March, she said.