Long History Of Terrestrial Life In NZ

27 January 2009

MEDIA RELEASE

Oldest Tuatara Fossil Lends Weight To A Long History Of Terrestrial Life In NZ

Latest research on the oldest tuatara (Sphenodon) fossils to have been found supports suggestions that the New Zealand landmass, once it had broken away from the super-continent Gondwana, had enough dry land to support early relatives of the tuatara, native frogs, and moa.

Recently, several scientists have argued that proto-New Zealand was completely submerged 22-25 million years ago, meaning that all terrestrial life would have had to arrive after that time. But Alan Tennyson, Te Papa’s Fossil Curator, says the age of these fossils, found in an ancient lake bed near St Bathans in Otago, suggests otherwise.

‘These three jaw fragments are between 16-19 million years old, and bridge a gap of nearly 70 million years in the tuatara fossil record,’ said Mr Tennyson. ‘A really diverse range of ancient fauna has been found at the St Bathans dig site, including many birds, mammals and reptiles. Coupled with evidence from several modern New Zealand invertebrates, it would seem that enough land remained for the survival of several animal lineages.’

'The alternative explanation that tuatara ancestors arrived here by ocean rafting seems unlikely. Modern tuatara can swim, but only short distances, and dehydration would be a serious problem,’ Mr Tennyson said. ‘Furthermore, there is no evidence of a population outside New Zealand at that time. The window of opportunity for colonisation has been greatly reduced by the discovery that ancestral tuatara were already here shortly after the supposed submergence.'

The article, published in the London-based Proceedings of the Royal Society late last week, was a collaboration between scientists from University College London, the University of Adelaide, and Te Papa. The St Bathans lake bed, estimated to be nine times the size of Lake Taupo, has been excavated over the past eight years. In 2006, scientists revealed that the remnants of a mouse-like mammal, and of at least 24 previously unknown extinct birds had been found.

The endangered tuatara (Sphenodon) is a reptile that has iconic status as the only survivor of a superficially lizard-like group that was globally widespread at the time of the dinosaurs. The tuatara lives on 35 islands scattered around the coast of New Zealand, mainland populations having become extinct with the arrival of humans and associated animals some 750 years ago.

Previously, the oldest known Sphenodon fossil dated to the Pleistocene era (around 34,000 years old), while the new discovery dates to the Early Miocene (19 to 16 million years ago). The new fossils are jaw fragments with the type and arrangement of teeth closely resembling those of present-day tuatara. They 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.

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