Griffith University PhD Candidate Meg Walker examines retrieved megafauna fossils from Engelbrechts cave in Mount Gambier, South Australia. Credit: Steve Trewavas

Distinct marks on cave bones can reveal how underwater fossil deposits formed and changed over time.

Deep inside flooded caves, animal bones can remain remarkably intact for decades or even centuries. Yet researchers have lacked a reliable way to determine how the remains of extinct megafauna and other animals accumulated in these submerged sites or how the cave environment changed them over time.

Research led by Griffith University now provides a framework for reading those clues.

“By analyzing animal bones from two underwater cave systems in South Australia, we have revealed how different cave environments leave distinct preservation ‘fingerprints’ on skeletal remains,” said Meg Walker, a PhD Candidate supervised by Australian Research Center for Human Evolution Director Professor Julien Louys.

“Backed by radiocarbon-dated bones, we tracked how skeletons accumulated and were modified over decades and centuries in underwater caves, then compared them to those buried in dry caves. Using a range of methods, from the macro to the micro, we looked at features associated with wet and dry caves. Things like spatial distributions of the bones and their surfaces, down to elemental compositions and proteins trapped in ancient cells.”

The team dives Kilsby cave. Credit: Steve Trewavas

Underwater caves leave distinct fingerprints

The comparison showed that submerged caves can preserve bones with exceptional clarity, retaining both their overall form and fine surface details.

At the same time, the water left behind distinctive chemical and biological evidence shaped by available light and the organisms living in each part of the cave.

Near illuminated entrances, algae and aquatic plants grew in the cave water and sometimes directly across bone surfaces, producing recognizable traces.

PhD Meg Walker inside Engelbrechts cave. Credit: Steve Trewavas

Farther inside, in completely dark zones where sunlight and plant life were absent, the bones remained largely untouched.

Dry cave remains followed a different path. They lacked the aquatic signatures and instead showed damage from land-based bacteria and long grooves formed by growing plant roots.

Recent remains help explain megafauna

Walker and her colleagues worked with specialist divers from the Cave Divers Association of Australia to collect historical animal remains from Green Waterhole and Gouldens Sinkhole near Mount Gambier in South Australia.

The collection included native and introduced species such as kangaroos, emus, dingoes, possums, quolls, swamp rats, cows, sheep, pigs, and rabbits. Some of the remains may date to the first European settlement of the area during the 1840s.

Some of the fossil fragments have lain hidden on cave floors for thousands of years. Credit: Steve Trewavas

By reconstructing what happened to these more recent bones, the researchers sought to understand how extinct megafauna remains entered the same underwater caves and what environmental conditions shaped their preservation.

A framework for submerged fossils

“This study has delivered the first framework for interpreting how megafauna fossils formed, survived, and changed in underwater caves,” Miss Walker said.

“It will provide archaeologists and paleontologists worldwide with a powerful new tool for reconstructing past environments and histories in these challenging conditions.”

Reference: “Neotaphonomic characteristics of vertebrate site formation in underwater caves” by Meg M. Walker, Joanne E. Wilkinson, Mathew Stewart, Geraldine E. Jacobsen, Shwaron Kumar, Vladimir Levchenko, Stewart Fallon, Rebecca Esmay, Rachel Wood, Justyna J. Miszkiewicz, Gilbert J. Price, Elizabeth Reed, Joseph Monks and Julien Louys, 15 July 2026, PLOS ONE.
DOI: 10.1371/journal.pone.0343896

Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.