Megafauna once roamed across Australia with some species reaching massive sizes. But ancient bone fragments are sometimes too damaged for palaeontologists to be able to assign them to a species – so they came up with a new way.

Better understanding species distribution through time could help determine why the megafauna vanished between 50,000 and 10,000 years ago. This in turn could give crucial insight into prehistoric ecosystems and help understand and even prevent future extinctions.

Palaeontologists are very good at looking at what to you and I seems to be a rock, and being able to determine it is a bone, which creature it belonged to and even when that animal lived. Developments in DNA extraction has improved their ability to pinpoint a species from ancient remains.

But what happens if a bone fragment is too old and damaged to tell what it is by comparing it to others and even DNA extraction?

A new study published in the journal Frontiers in Mammal Science shows how peptides – short chains of amino acids which make up protein molecules in animals – found in the collagen of ancient bones can be used to work out which species it comes from.

“Proteins generally preserve better over longer timescales and in harsh environments than DNA does,” says first author Carli Peters from the University of Algarve in Portugal. “This means that in the context of megafauna extinctions, proteins may still be preserved where DNA is not.”

The scientists studied 3 large extinct Australian megafauna: Zygomaturus trilobus, Palorchestes azael, and Protemnodon mamkurra.

All 3 species went extinct within the last 50,000 years – surviving long enough to have overlapped with humans arriving on the continent. P. mamkurra may even have survived long enough to have been seen by humans arriving in Tasmania.

“Zygomaturus trilobus was one of the largest marsupials that ever existed – it would have looked like a wombat the size of a hippo,” explains senior author Katerina Douka from the University of Vienna in Austria. “Protemnodon mamkurra was a giant, slow-moving kangaroo, potentially walking on all fours at times. Palorchestes azael was an unusual-looking marsupial that possessed a skull with highly retracted nasals and a long protrusible tongue, strong forelimbs, and enormous claws. If the early modern humans who entered Sahul – the palaeocontinent that connected present-day Australia, New Guinea and Tasmania 55,000 years ago – came across them, they would have certainly got a big surprise.”

For more on Palorchestes azael, read the Cosmos magazine feature, “Victoria through prehistoric time.”

“The geographic range and extinction date of megafauna in Australia, and potential interaction with early modern humans, is a hotly debated topic,” says Douka.

“The low number of fossils that have been found at paleontological sites across the country means that it is difficult to test hypotheses about why these animals became extinct,” Peters adds.

Studying amino acid chains could help, according to Peters.

“Zooarchaeology by mass spectrometry – ZooMS – could increase the number of identified megafauna fossils, but only if collagen peptide markers for these species are available.”

The team used ZooMS to differentiate Protemnodon from 5 living genera and 1 extinct genus of kangaroos. They were also able to distinguish Zygomaturus and Palorchestes from other living and extinct large marsupials, but they couldn’t differentiate the 2 species from each other. Unless further research allows for more specificity, these markers are best used to identify bones at the genus level rather than the species.

“By using the newly developed collagen peptide markers, we can begin identifying a larger number of megafauna remains in Australian paleontological assemblages,” says Peters. “However, there are a lot more species for which collagen peptide markers still need to be characterised. Two examples would be Diprotodon, the largest marsupial genus to have ever existed, and Thylacoleo, the largest marsupial predator.”