Ancient find in Aussie desert sheds light on 130-year-old European mystery

An ancient find in Australia’s outback has helped shed light on mysterious items that have confounded European experts almost 15,000 km away. “It’s been a big puzzle,” paleontologist Dr Carole Burrow told Yahoo News.

She’s been leading an investigation into a collection of tiny bones dug up 14 years ago in Queensland, near the Northern Territory border. Dated at 400 million years old, the fossils belonged to a species of long-extinct fish that thrived in the region’s shallow saltwater environment before the landscape dried up and turned into a red desert.

The only place similar bones have been found is Scotland where remains of the mysterious fish are quite common. But the fossilisation process there has frustratingly resulted in most of the bones being squashed flat, and that’s made it hard for researchers to study them. It has led to wrong conclusions about the fish. Initially, it was thought to be a jawless fish that was found nowhere else in the world.

What’s different about the Australian fish bones, is that despite being 10 million years older, the fossils have been very well preserved at the Cravens Peak dig site. Burrow, who is an honorary fellow at Queensland Museum, worked with an international team to analyse a tiny fossilised braincase that was preserved as a three-dimensional specimen inside a rock.

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While it’s similar to the Scottish fish, the researchers determined the bones belonged to a new species of jawed vertebrate, likely a distant relative of sharks. Their findings about the fossils were published in the journal National Science Review.

“With radically different interpretations of its structure, it has been assigned to almost all major jawless and jawed vertebrate groups,” the paper says of the Scottish species. It then highlights new analysis of how its eye sockets and jaw likely evolved, helping to build a picture of its appearance.

Paleontologists mystified by elusive fish for 140 years

Named palaeospondylus australis, the Queensland find marks the first time the genus has been found outside Scotland. It’s there that the closely related palaeospondylus gunni was discovered in 1890, mystifying researchers because of its unique skeletal features and uncertain classification.

“There are thousands of specimens of the Scottish species around the world in museums, but because all the bits of the fish have melded into each other you can’t work out which are the separate bits. It’s hard to know which bit is the neurocranium, the braincase, or the jaws,” Burrow said.

“People have been speculating for the last 130 years about what it might be. And it’s been a puzzle for people ever since it was first described.”

Why is the fish only in Scotland and Queensland?

The reason Palaeospondylus remains are only found in Scotland and Australia is likely simple. The fish could have been widespread around the world, but the conditions weren’t right to fossilise the tiny bones anywhere else.

“It’s unlikely to have been preserved in anything other than really specialised environments — totally different environments as it turns out,” Bowen said.

“Because in Scotland, it’s supposed to have been found in a freshwater deposit — but it must have had a marine connection at times. And in Queensland, it’s marine.”

What did the fish look like?

Although researchers know the bones are from two similar species, little is known about how the fish looked. One key reason is that its a paedomorphic fish, meaning it’s kept a lot of juvenile or even larval characteristics into its later life.

“It doesn’t have any dermal armour, it doesn’t have scales, it doesn’t have bones on the outside — there’s only the endoskeleton of the fish,” she said.

“So it’s still a mystery fish.”

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