Dinosaur prints confirmed: Whanganui Inlet reveals a New Zealand first
Geologist Dr Greg Browne and a 70 million-year-old dinosaur footprint in sandstone rock in Whanganui Inlet. Photo: Supplied.
Seventy-million-year-old dinosaur footprints found in rocks at Whanganui (Westhaven) Inlet have made national news headlines following official confirmation described as “hugely exciting”.
They are believed to be the first dinosaur footprints recognised in New Zealand, and the first evidence of dinosaurs in the South Island.
Geologist Greg Browne of GNS Science originally discovered the footprints over repeated visits during the 1990s while investigating the properties of the rock and sediment formations in Whanganui Inlet. The public announcement coincides with the recent release of a scientific paper on the find. An article will appear in the New Zealand Journal of Geology & Geophysics this December.
Dr Browne said it had taken him this long to carefully consider all the possible geological and biological explanations for the features, and then rule them out one by one before submitting his conclusions to peer review. His investigation had to include comparisons with dinosaur footprints in similar-aged rocks in other parts of the world.
The footprints are in six undisclosed locations on both public and private land in an area about 10 kilometres long. At one location, there are about 20 footprints.
The most plausible explanation is that the markings were made by sauropods – herbivorous dinosaurs between 2m and 6m in length, with long necks and tails, pillar-like legs and a weight of several tonnes. The depressions are roughly circular, with the largest about 60cm in diameter, though most span 10cm to 20cm. Clear “toe ends” and “heel ends” can be seen, indicating the direction of travel.
Dr Browne said the footprints were made in intertidal beach sands and were probably quickly covered and preserved by mud from subsequent tides. Northwest Nelson was largely submerged by 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. New Zealand has since been uplifted and northwest Nelson has re-emerged. During the past 20 million years, the overlying sedimentary rock has eroded and exposed the footprints.
“It’s absolutely amazing that they’re here in the first place, because an intertidal environment is somewhere where structures get destroyed very quickly, by wind, or by tides, by currents, by waves – so the chance for preservation is very slender.”
Scientists have taken casts and are working to preserve the prints, which are eroding, though erosion may yet expose more prints, they acknowledged.
Dr Browne is away on an extended overseas assignment, but 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.”
Paleontologists know that dinosaurs were present in ancient New Zealand, but evidence has been slow to surface. Dinosaur bones, mostly vertebrae, have only been found at three locations, in northern Hawkes Bay, Port Waikato, and the Chatham Islands.
Dr Joan Wiffin discovered this country’s first dinosaur fossils in 1974, and Englishwoman Mary Ann Mantell found the first complete fossil bone recognised as that of a dinosaur.
Dr Browne said the latest 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.”
Gerard Hindmarsh
