Ancient bones deposited in submerged caves offer researchers rare and powerful insight into the past.
Yet until now, they have struggled to understand how the remains of expired megafauna and other animals find their way into such watery graves.
To unlock the mystery, Griffith University experts have spent the past several years exploring some of the world's most spectacular subterranean networks near Mt Gambier, on South Australia's Limestone Coast.
Initiated by renowned palaeontologist Julien Louys in 2023, the project has more recently featured the work of PhD candidate Meg Walker, under his supervision.
Her focus has been bone rooms in two cave systems that have revealed how different environments leave distinct "fingerprints" on skeletal remains.
"We tracked how skeletons accumulated and were modified over decades and centuries ... then compared them to those buried in dry caves," Ms Walker explained.
"Things like spatial distributions of the bones and their surfaces, down to elemental compositions and proteins trapped in ancient cells."
The results were clear: wet caves often preserved bones remarkably well, maintaining their structure and surfaces in exquisite detail.
Submerged chambers also leave unique chemical and biological traces shaped by types of algae and plants growing near bright entrances.
In the so called midnight regions of the caves, though, where light never reaches and no plants grow, the researchers found bones stayed pristine.
In contrast, remains found in dry caves didn't exhibit the same signatures and were eaten by bacteria and marked by plant roots.
Specialists from the Cave Divers Association of Australia assisted with the retrieval of material.
They plunged into the gloomy depths of Green Waterhole and Gouldens Sinkhole, two of more than 800 underground time capsules carved into porous limestone in the region.
The remains of both native and domestic animals were recovered.
Everything from cows and kangaroo bones to those belonging to emus, sheep, pigs, dingoes, rabbits, possums, quolls and swamp rats.
It was determined some of the non-native specimens likely dated to European settlement of the Mount Gambier area in the late 1840s.
But Ms Walker hopes the work will also shed light on far older scientific enigmas.
"The study has delivered the first framework for interpreting how megafauna fossils formed, survived and changed in underwater caves," she said.
"It will provide archaeologists and palaeontologists worldwide with a powerful new tool for reconstructing past environments and histories in challenging conditions."
For Professor Louys, the inaccessibility of the caves is both a blessing and a curse.
Fewer people have entered some of the claustrophobic caverns than have set foot on the moon, leaving the fossils within unmolested for millennia.
By further studying the preserved remnants, he hopes to reconstruct prehistoric settings and advance understanding of why creatures died out.
"Palaeontology is more than studying dinosaur bones," he told AAP shortly after beginning his quest in 2023.
"Where the fossils come from, their context, age and relationship to other fossils is critical information we use to understand past environments and how climate change impacted ecosystems in the past.
"That's one of the most long-ranging debates in Australian palaeontology and global palaeontology, what happened to these megafauna?"
The beasts, which included wombats weighing more than a tonne and an echidna the size of a sheep, vanished towards the end of the Pleistocene era 12,000 years ago.
Ms Walker's findings have been published in research journal PLOS One.
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