Mysteries of prehistoric Australia: a tough place to hunt dinosaurs and megafauna

Excavating a diprotodon at Cox’s Creek in northern NSW. AAP/South Australian Museum.

The harsh, flat, ancient, vastness of Australia is an unforgiving place for palaentologists.

The pickings can be much richer in more mountainous and rocky regions of the world, a difference highlighted by the often bountiful research conducted in such places as Wyoming and Utah.

A new paper from researchers working in the Morrison basin area of those western US states, gives evidence to theories that even enormous dinosaurs migrated long distances.

Researchers led by Associate Professor Henry Fricke, chair of geology at Colorado College, examined enamel from teeth that were last chewing up to 160 million years ago and published their findings yesterday in Nature.

The teeth belonged to specimens of the Camarasaurus sauropod, a late Jurassic herbivore that could weigh 47 tonnes and grow 23 metres in length.

Fricke’s team measured oxygen isotopes in the enamel. As the sauropods’ teeth grew in their youth, the animals’ drinking water would leave its trace in the isotope ratios. The water would likewise leave its trace in rocks of the area, so by comparing the two, the researchers were able to tell how far the remains were from where where they drank water in their youth. The distances ranged up to 300 kilometres from highlands to the Morrison basin in Utah and Wyoming.

Research can be much more difficult for palaeontologists in Australia, where conditions are less than ideal.

Professor Patricia Vickers-Rich, a palaeontologist and the director of the Monash Science Centre, explained some of the difficulties of working on this continent.

“In Australia we don’t have a lot of stuff. It really is hard to find this material [fossil remains],” said Professor Vickers-Smith, who has a special interest in Australia’s polar dinosaurs.

“We’ve worked on these polar dinosaurs for 30 years to get what we’ve got, and I think the last calculation we made that over 30 years we’ve managed to find about 18,000 bones that you can do anything with - and that doesn’t give enough information. They’re fragmentary and hard to find and it’s just very difficult,” she said.

Mountains and rock-outcrops are ideal for finding fossils because their sides and sections can display fossils. But the great southern land has a relative dearth of these land formations.

“Australia has been a very flat continent for a very long time, and we don’t have much in the way of outcrop during the Cretaceous (145 million years ago to 65 million years ago] and early Tertiary [about 65 million years ago]. Out early Tertiary record, which is the record right after the dinosaurs go extinct, is almost nonexistent because we just haven’t found the stuff,” she said.

Asked if Australia was under-studied, Professor Vickers-Rich said it was more a case of being “under-prospected”.

“We need to prospect more and more and more for these sites. There are a lot of isolated areas that we just haven’t gotten into, but in addition it’s under-geologised in the sense that we just don’t have the outcrops here like we’ve do in Canada or South America or Asia. You go to Mongolia and you can walk for hundreds and hundreds of kilometres and there’s just outcrops [everywhere] with fossils in them, and there’s mountains there that push stuff up and you can see long sequences with fossils in them,” she said.

“But here, our mountains are on the east coast where they’re covered with trees - therefore you can’t really find very much. If you go into the interior, there’s no mountains and very little topography and a lot of its covered with sand - the fossils are in rocks that are underground and you can’t see them,” she said.

“We have this unfortunate topography and unfortunate trees in places where you might be able to find stuff - it’s just covered with vegetation. Whereas in Mongolia it’s not the case. In western Argentina it’s not the case - you’ve got a big mountain range and you’ve got lots of dry arid areas where things crop-out and you can go prospecting,” she said.

“You’ve got to have exposure and ou’ve got to have it in dry areas. To palaeontologists when you’ve got mountains in tropical regions they’re not very use, because they’re covered with beautiful vegetation - which we all want - but if you’re a geologist you want to look at the rock, so you have to go to quarries or river cuts,” she said.

Many of Australia’s fossils are hidden underground, but many would also have been destroyed by some of the elements that define the country’s landscape.

“Australia’s not always been where it is now, and when it was further south there was a lot of water and a lot of leeching went on. A lot of the red soil that we find in Australia means that if you had bones in sediments like that they probably would have been dissolved,” she said.

“So we’ve got this problem of chemical weathering and lack of topography and lack of out-crop, and we’ve got another problem that some of the out-crops are in very remote and isolated areas,” she said.

“This is a problematic continent.”

The diprotodon: one of Australia’s megafauna. It could grow to two tonnes and is believed to have been hunted to extinction by Australia’s early inhabitants 30,000 to 40,000 years ago. AAP/South Australian Museum

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