Mystery bird fossil found in the Nullarbor

By Campbell Phillips 16 August 2011
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An expedition into the Nullarbor has uncovered a hoard of fossilised birds, including one that is 780,000 years old. But what is it?

WHEN A TEAM OF SPECIALISTS from Flinders University and the Western Australian Museum last week unearthed dozens of bird bones in Leaena’s Breath Cave – in the Nullarbor Plain near the border of WA and South Australia – one specimen proved to be particularly interesting.

Dr Gavin Prideaux of Flinders University was excited by the size and relative completeness of the fossil, and quickly sent pictures off for expert appraisal. He was even more excited to learn that the fossil was potentially that of a prehistoric wedge-tailed eagle.

“We’ve only ever found one partial [wedge-tailed] eagle fossil before so, given how complete this specimen is, it would be an exciting discovery,” Gavin said from the field this week. “We’ll need to get the specimen back to Flinders University to determine whether it is an eagle and, if so, whether it is the same species as the modern wedge-tailed eagle or something new.”

Missing pieces

The initial pictures that Gavin took of his find had been sent to Dr Trevor Worthy, the only specialist avian palaeontologist in Australia. Trevor made the initial identification of a wedge-tailed eagle, but when Australian Geographic contacted him with more images on Monday, he realised he had missed something.

“This is an interesting example that demonstrates the potential pitfalls of trying to identify fossils remotely,” says Trevor. “The truth is, anyone can make errors when trying to identify things in the field, covered in dirt or only partly exposed, or in this case when examining snapshots of bones…Nothing beats having specimens in your hand in the lab.”

The fossil that was at first tentatively identified as an eagle skeleton turns out to be an extinct, flightless bird called progura, a giant version of the modern malleefowl. “I changed my mind when I saw an image that contained the lower leg bone,” he says. “Previously, I had based my identification on the size and an aspect of the wing bone, which in this species shares similarities with the wing bones of eagles.”

Gavin Prideaux of Flinders University with the fossil bones. (Credit: Clay Bryce)

Avian graveyard

The identification of this fossil as progura is significant, as Leaena’s Breath Cave is a long way from the other locations where the species has been found. “The closest examples of progura were found in a cave on Yorke Peninsula [SA] and a site on the Warburton River [SA],” says Trevor. “This particular discovery represents a major extension of the known range of this bird.”

Leaena’s Breath Cave, 70km west of the South Australian border, is noteworthy due to the sheer age and extent of the collection of bird remains that have been found there.

“This cave has been acting as a bird death trap for at least a million years,” says Gavin. “Surrounding these larger bones are literally hundreds of songbird bones, a situation mirrored through the rest of the deposit.”

The discovery of the new fossil was made only two days into the expedition, which is still ongoing. Videos and blogs documenting the expedition can be found here.