Oh, baby.

The discovery of a one-month-old tuatara, a rare reptile descended from lizard-like dinosaurs, has conservationists in New Zealand celebrating. The critter is the first baby tuatara to be spotted on the mainland there in two centuries, since zoologists released 200 adults inside the Kaori Wildlife Sanctuary beginning four years ago in the hope they'd reproduce.

"We are all absolutely thrilled with this discovery," the sanctuary’s conservation manager, Raewyn Empson, said in a statement. "It means we have successfully re-established a breeding population back on the mainland, which is a massive breakthrough for New Zealand conservation."

The reptiles were taken to Kaori to protect them from predators and give them a wider habitat and protection from global warming (tuatara gender is determined by soil temperature). Finding the baby isn’t entirely unexpected; the sanctuary reported in October that it had spotted a tuatara nest with four eggs.

Tuatara are classified as vulnerable by the International Union for Conservation of Nature and Natural Resources (IUCN). They’re native to New Zealand and the only living members of the order Sphenodontia. Because other species in the order became extinct 60 million years ago, tuatara are often called “living fossils,” the sanctuary notes. While it’s unknown how long they’ve been absent from the country’s mainland (they do live on surrounding islands), they had virtually disappeared by the late 1700s after the kiore, or Pacific rat, ate their eggs.

Some fun tuatara facts, per the sanctuary: They grow up to 24 inches (60 centimeters) long and 2.2 pounds (1 kilogram), and are known for their “third eye,” a patch of white scales at the top center of their skull. The reptile can’t actually see out of it, but the “eye” may act as a light sensor, telling the animal how much time to spend in the sun. It tends to be visible only in the first six months of a tuatara’s life.

Tuatara can hold their breath for up to an hour, and also have unusual teeth – a single row on their bottom jaw, and a double row on the top. And their longevity is better than most of ours: tuatara are thought to live for about 100 years.

Image of baby tuatara/Tom Lynch, Karori Sanctuary Trust