Science

Fossil suggests New Zealand did not drown

A tuatara
Thursday, 22 January, 2009

The discovery of the fossil of a lizard-like New Zealand reptile dating back 18 million years has sparked renewed debate over whether the continent was fully submerged some 25 million years ago.

The endangered New Zealand tuatara (Sphenodon punctatum) is a lizard-like reptile that is the only survivor of a group that was globally widespread at the time of the dinosaurs. The tuatara lives on 35 scattered islands around the New Zealand coast. Populations on the mainland became extinct after the arrival of humans and their associated animals about 750 years ago.

In a paper published this week in the journal Proceedings of the Royal Society B, a team of British, Australian and New Zealand scientists says its findings offer further evidence that the ancestors of the tuatara have been on the landmass since it separated from the rest of the prehistoric southern super-continent of Gondwana about 82 million years ago.

The oldest known tuatara fossil is only about 34,000 years old. The new fossil discovery dates to the Early Miocene (from 19 to 16 million years ago). Its jaws and teeth closely resemble those of the present-day tuatara, so it appears to bridge a gap of nearly 70 million years in the fossil record of the group between the Late Pleistocene of New Zealand and the Late Cretaceous of Argentina.

Lead author Dr Marc Jones, of University College London, said: "It has been argued that New Zealand was completely submerged during the Oligo-Miocene drowning of the continent some 25 to 22 million years ago. However, the diversity of fossils now known from the Miocene (St Bathans Fauna of the Manuherikia Group) suggests it is more likely that enough land remained above the water to ensure the survival of a number of species, such as frogs, kauri trees and several modern freshwater insects, as well as the tuatara."

The research team involved scientists from the Museum of New Zealand Te Papa Tongarewa and Dr Trevor Worthy of the University of Adelaide, who is now with UNSW.

Media contact:
UNSW Faculty of Science - Bob Beale 0411 705 435 bbeale@unsw.edu.au

Original UCL media release is here.