Scientists find dinosaur footprints

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EXCITING DISCOVERY: Greg Browne with one of the dinosaur footprints.

Queensland Museum

ONCE UPON A TIME: An artist's impression of what a sauropod would have looked like. These enormous plant-eating creatures were roaming New Zealand 70 to 80 million years ago.

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Scientists say they have found 70 million-year-old dinosaur footprints in Golden Bay, which they believe are the first dinosaur footprints to be recognised in New Zealand, and the first evidence of dinosaurs in the South Island.

Geologist Greg Browne of GNS Science found the footprints while investigating the properties of the rock and sediment formations in Whanganui Inlet.

He said they were in six locations spread over an area about 10 kilometres long. At one location, there were up to 20 footprints.

Dr Browne said he carefully considered all the possible geological and biological explanations for the features in the rock, and was able to rule them out one by one.

His investigation included comparisons with dinosaur footprints in similar-aged rocks in other parts of the world.

He concluded that the most plausible explanation was that the markings were made by sauropods – large herbivorous dinosaurs with long necks and tails and pillar-like legs.

Paleontologist Dr Hamish Campbell of GNS Science said: "This is hugely exciting. It gives us food for thought and we will now go and examine rocks of comparable age."

Dr Browne said the footprints were made in beach sands and were probably quickly covered and preserved by mud from subsequent tides.

"What makes this discovery special is the unique preservation of the footprints in an environment where they could easily have been destroyed by waves, tides, or wind."

The depressions are roughly circular, with the largest about 60cm in diameter. Most are smaller, typically between 10cm and 20cm in diameter and were probably formed by dinosaurs between 2m and 6m in length and weighing several tonnes.

While paleontologists know that dinosaurs were present in ancient New Zealand, which they refer to as Zealandia, the record of their presence is sketchy.

Dinosaur bones, mostly vertebrae, have been found at three locations, in northern Hawkes Bay, Port Waikato, and the Chatham Islands.

Dr Browne said the footprints added a considerable amount of information about how dinosaurs moved, how fast they moved and how big they were, as well as how soft the sediment was.

"This discovery opens the way for further study on a range of dinosaur-related issues in New Zealand."

Northwest Nelson was largely submerged under the sea between 70 and 20 million years ago and the footprints would have been covered by hundreds of metres of marine sediments, he said.

With the development of the modern plate boundary, New Zealand was uplifted and northwest Nelson emerged from the sea. During the past 20 million years, the overlying sedimentary rock has been eroded to expose the footprints.

Dr Browne's discovery will be published in next month's New Zealand Journal of Geology & Geophysics.