Ancient links: Articulated hand of the predatory dinosaur Megaraptor namunhuaiquii from the mid-Cretaceous of Argentina superimposed on several paleogeographic maps of the mid-Cretaceous.

Credit: Nathan Smith, Field Museum

Related articles

• Australia's largest ever dinosaur unveiled
• Odd predatory dinos share features with hyena and shark
• Did bugs bring down the dinosaurs?
• Large flock of parrot-like dinosaurs uncovered
• Meteor mega-hit spawned Australian continent: researchers

SYDNEY: A fossilised bone originally found 20 years ago may hold the key to the enigmatic origins of Australia’s dinosaurs, a new project has found.

The dinosaur's upper arm bone, found in Australia, shows strong similarities to the carnivorous dinosaur Megaraptor, which was previously only known in South America. It is the first fossil evidence to confirm a link between Australia’s dinosaurs and those of another southern continent, and suggests the creatures migrated across the ancient super-continent, Gondwana.

“We’ve been waiting a long while for evidence like this,” said palaeontologist Steve Salisbury, from the University of Queensland in Brisbane. “And it’s incredibly lucky - if we had to name any single bone that could help us identify Megaraptor and kin, the forearm bone we have would be it. It is very distinctive and unlike that of any other dinosaur.”

North or South?

In the past, Australian dinosaurs of the Cretaceous Period (beginning 145 million years ago) have only been tentatively compared to those found in the Northern continents, but not Southern.

This has always been considered problematic, Salisbury said, since Australia was not linked to the northern landmasses at this time. Instead, Australia was part of the supercontinent Gondwana, which, in addition to Australia, comprised South America, Africa, Antarctica, India, Madagascar and New Zealand.

The new fossil, found at Dinosaur Cove on the coast of the southern Australian state of Victoria, is starting to clear things up, Salisbury said. “It confirms that dinosaurs were actively moving across and between the continents that made up Gondwana – and so yes, it is likely some of our dinosaurs, or their ancestors, arrived here from South America.”

The dinosaur, is described this week by a team including Salisbury and Nathan Smith of the Field Museum in Chicago, USA, in the British journal, the Proceedings of the Royal Society B.

It also dispels the idea that Australia was somehow isolated from the rest of Gondwana during the period, either by geography or climate, as previously considered.

Piece of the puzzle

“We’ve always thought that faunal exchange [the movement of dinosaurs] was happening across Gondwana, between Australia and South America, but here is our proof of the idea,” palaeontologist Robert Jones, from the Australian Museum in Sydney, said of the research.

But we haven’t solved a revolutionary puzzle just yet, he warned. “The problem here is that we’re only talking about an isolated bone, a fragment of one animal, so realistically there’s only so much we can suggest from it.”

The authors of the study agree – but are hopeful more proof is on the way. “In recent years we’ve had many fossil discoveries in areas that were once part of Gondwana,” Salisbury said. “We need to be checking out the details of these closely, because that’s probably where we’ll find the answers to exactly what types of dinosaurs occurred in Australia.”