Big feet to follow

NAOMI ARNOLD traces the footsteps of Golden Bay's dinosaur discovery.

It's a long way from anywhere, the Whanganui Inlet, a lonely, windswept world of sand, rock, tide and mud tucked into the west coast of Golden Bay.

Surrounded mostly by native forest with just a few settlements on its edges, it is home to a handful of people and popular with more enthusiastic tourists, and once, we now know, it was a land of dinosaurs.

Two weeks ago, Geological and Nuclear Sciences (GNS) scientist Greg Browne announced that he had discovered New Zealand's first-ever evidence of dinosaur footprints. It wasn't long ago that everyone believed dinosaurs had never existed in New Zealand before. Perhaps it was just that no-one had been looking.

Like our first dinosaur fossil discovery in the late 1970s, this story has a typically Kiwi ring to it. In the mid-1990s, Dr Browne, a lone sedimentologist, found a set of marks in the rocks of Whanganui Inlet and was intrigued.

In six locations spread over 10 kilometres, the marks were roughly oval, with some up to 60 centimetres across.

With no money for funding, Dr Browne investigated in his own time when work returned him to the area. The mystery of the marks continued to intrigue him, and during the next 15 years, he carefully eliminated every possible cause, until there was only one left that made sense.

The news was an immediate sensation, spreading around the world. Radio New Zealand presenter Kim Hill claimed the honour of breaking it. GNS communications manager John Callan recalls that on learning of the discovery, Hill immediately said: "You can stay in my bach if you give me the exclusive".

Because the expedition was unfunded it saved on accommodation costs. As soon as Hill announced the news, it was around the globe.

It was big news. Dr Browne's discovery was the first proof of dinosaurs in the South Island, and the only footprints ever found in New Zealand.

There are just three dinosaur bone fossil sites in the country – in the Chatham Islands, northern Hawke's Bay and Port Waikato.

Until recently, everyone believed that Zealandia, the continental fragment that became New Zealand, drifted apart from Gondwanaland before dinosaurs reached it. The general wisdom was that New Zealand had been underwater when the massive reptiles roamed the Earth. As a result, our vertebrate palaeontology was a minor pursuit reserved for enthusiasts.

Regardless, in 1975, one of those enthusiasts, a middle-aged amateur palaeontologist named Joan Wiffen, went exploring. She stumbled across a broken fossil in northern Hawke's Bay, unlike anything she had ever seen before.

Her chance discovery was confirmed as a 65-million-year-old vertebra, the tail bone from a small, three-toed meat-eater and New Zealand's first dinosaur.

Dr Browne's find is similarly serendipitous. He has spent many hours of his working life in northwest Nelson, hunting for oil and gas. As well as being home to some of the oldest rocks in New Zealand, the area is formed from the source rock for most of our oil and gas reserves – the Cretacean North Cape Formation, laid down about 45.5 million to 65.5 million years ago. Back then, the area was a flattish coastal plain with wide, lazy rivers, at a much higher latitude than it is now.

Dr Browne spoke to the Nelson Mail on a one-day layover in Wellington, between weeks spent at sea drilling off the coast of Canterbury and Queensland.

He explained how he had thought about the marks for years after he first found them.

"It was hard to explain by physical processes," he said.

"When you see something you can't make sense of, you start to wonder."

They couldn't have been caused by tides, winds or currents, he reasoned, because some of the edges were sharp and their size was too consistent. Most telling of all, the material underneath the prints, viewed in cross-section, had been deformed and compressed, as though a heavy weight had been placed on top.

That left animals. But he ruled out the possibilities one by one. They couldn't be the remnants of feeding or resting fish, because the marks were deep, and fish weren't heavy enough to cause the curious compression underneath. They weren't big enough to be the prints of other Cretacean amphibians or birds.

In cross-section, they looked similar to the footprints of modern animals, but there were no known mammals in Zealandia at the time that could have left them.

Preserved on top of the club-like prints were little blocks of sand and mud, perhaps left behind from where a foot had lifted off. There were clear heel-toe depressions, like the ones we'd find behind us walking across a beach. The foot, big and broad, must have held up a large, heavy animal, weighing several tonnes.

In other words: dinosaurs – sauropods, specifically, the dominant herbivores at the time, the type of dinosaur a child might draw, with a small head, long neck and tail, a big body, and big, wide feet well suited to swampy environments.

The prints have no claw marks, nothing that would indicate a fast-running carnivore.

Instead, as Dr Browne told Hill, the prints look rather like those of a cow or horse – a large but innocuous plant-eater.

He has further classified them as titanosaurs, but that's as far as he has got down the family tree.

Mrs Wiffen found a single titanosaurian vertebra from the early Cretaceous in inland northern Hawke's Bay, and Dr Browne assumes it was a similar creature that tramped across the beach sand 70 million years ago.

It was an accident of time, mere chance that they were preserved. Dr Browne surmises that straight after the animals left the prints, a sticky mud oozed over them, preventing them from being destroyed by water and wind.

Nelson Provincial Museum chief executive and dinosaur enthusiast Peter Millward says there has always been speculation that there were dinosaurs in Golden Bay, but the fact that Dr Browne found anything is "absolutely incredible".

"Our geologic history has been up, down, under water, broken up, volcanic stuff over the top of it, broken down, eroded – our landscape's been pulverised, whereas there are parts of China, where there are tens of thousands of sites that have been virtually untouched for the last couple of a hundred million years."

Despite the news media's initial excitement at the news, GNS and Te Papa geologist Hamish Campbell expect the scientific world will take several months to whip up a fervour, because the December issue of the New Zealand Journal of Geology and Geophysics is not yet out.

"Scientists tend to trust the literature rather than the media reports," he says.

But he believes the discovery has added considerably to the tiny pieces that make up the puzzle of the Earth as it was 70 million years ago. Dinosaur fossils are rare in the southern hemisphere and every little bit helps the collective knowledge.

"We can now be certain that these dinosaurs were on Zealandia, so we must be dealing with dinosaurs that had evolved remotely from dinosaurs on Gondwanaland, for some period of time. They would have been Zealandian dinosaurs, of which we know very little. These are important internationally, and it's confirmation that [dinosaurs] really were everywhere there was land."

Dr Browne is convinced, as are his colleagues, but he is happy to be proven wrong in the spirit of scientific discovery.

"It's something that people can debate. Based on the evidence, they can make their own decisions, but we'll go through a process and discussion. We put out ideas, people criticise those or review them and that's accepted.

"For all I know, there could be something which points to something else."

Once the journal has been published, experts will likely come from overseas and "we'll learn a lot more".

As to where they are in Whanganui Inlet, Dr Browne will only drop tantalising clues. The prints are in the inter-tidal zone, under Conservation Department control, although some border private property. The location is so secret that even the locals don't know about them, he says.

There's certainly an enthusiasm to find out. As Farewell Spit Tours operator Paddy Gillooly told the Motueka-Golden Bay News: "If the footprints are easily accessible we'd definitely stop and look as part of our tour."

That's exactly the sort of thing Dr Browne fears, a surge of souvenir hunters wanting to pinch their own little piece of dinosaur lore. Instead, he hopes that displays of casts in museums will satisfy the public's curiosity.

He admits ownership is a tricky question.

"It's part of our natural heritage, I know. It's a site where perhaps another country would turn it into a reserve or national park or whatever, but it's not going to get to that level in New Zealand, obviously. It's a delicate site in that they'll ultimately be eroded by the sea as well. It's going to be a compromise whatever decision you make."

The possibility of fencing the sites was considered, but discarded.

"Again, that would attract people's interest. At the end of the day if people are determined nothing much in the way of a physical structure would necessarily stop that. But the way we've decided to do it, rightly or wrongly, is to limit access only to bona fide researchers."

He cites Trilobite Rock, an isolated limestone outcrop in the Cobb Valley that contains the oldest fossils in New Zealand. "People go up there and chip away at it. It gets smaller and smaller and if every tenth person takes a sample there's nothing left."

Peter Millward echoes the concern. "People discover things in caves and they don't stop and think about [that] if you take it away from the context in which it originally existed you lose so much information. This is what happens with material that gets handed in at the museum. Some people come in and drop something on the counter and literally run for the door. They think `they'll look after it', but if we don't know where it came from or who it belonged to ... the story that goes with it is so fabulous."

Mr Millward wants only to get his hands on some kind of mould for the museum, in place for the Christmas holidays. Just to show the kids, of course. And like a schoolboy, he's eager that more traces of dinosaurs will turn up.

"One can be almost certain that if there's one bone or one footprint found then there must be thousands," he says, with relish. He imagines a great clutch of eggs nestled somewhere beneath the earth, like the titanosaur nests found in Patagonia in 2001.

"If there are footprints and bones and everything else, it is not impossible that somewhere in New Zealand there is a layer of rock which might break open tomorrow and reveal a heap of dinosaur eggs," he says. "There's absolutely no reason why that couldn't occur."

He believes that now some footprints have been found, there's the possibility that previously overlooked marks in rocks around the area might turn out to be remnants of dinosaurs as well. He draws on the example of Ferdinand von Hochstetter, the German geologist who surveyed New Zealand in 1858 and immediately saw fossils embedded in the rocks above Richmond – because he knew what to look for.

"You put on a set of lenses. What do they say? `Chance favours the prepared mind'." Browne's discovery was "a really brilliant" example of that.

"There was someone who was prepared to accept the possibility that dinosaurs might have walked the land in this region, and what he's discovered is going to rate up there as one of the dinosaur finds. It makes you wonder whether there aren't lots and lots more of these sorts of things, but you don't recognise them so you don't know what their significance is."

It could be said that like Dr Wiffen, Dr Browne has now re-written the geologic history of New Zealand. He also hopes that people will take a closer look at what evidence of dinosaurs they might have at the bottom of the garden.

"There could be more," he says with a note of excitement. The appearance of several sets of footprints scattered throughout different locations in Whanganui Inlet suggests they're not actually that uncommon. There could be bones, fossils, fragments – more traces of the great beasts that lumbered through the estuaries of Golden Bay 70 million years ago. A set of tracks would be the ultimate clincher.

But right now, there are only a few people out there looking for them.

- © Fairfax NZ News