Behind the scenes of facial muscle research in Western Australia’s fossil koalas

Associate Professor Natalie Warburton

My recent publication in R Soc Open Sci. https://doi.org/10.1098/rsos.251572 with Dr Kenny Travouillon and team at the WA Museum has generated excitement in the palaeontology world with the discovery of a new fossil koala from the Pleistocene of Western Australia. While the fossil itself provides invaluable clues about the morphology of ancient marsupials, the research team went a step further to decode the evolutionary story: we dissected a modern koala to understand its facial muscles, bridging the gap between past and present.

But how does dissecting a living species help us interpret fossil remains? The answer lies in comparative anatomy. Fossils often preserve bones, but rarely soft tissue. Muscle attachment sites, however, leave subtle marks on bone surfaces. By examining the facial musculature of a modern koala, we can hypothesise how muscles might have been arranged in the fossil specimen, offering insights into its feeding habits, vocalisations, and expressions.

Ethical sourcing was paramount in this study. The koala used for dissection was part of a managed population and had been humanely euthanised due to old age. This ensured the research was conducted respectfully, minimising impact on wild populations and maintaining high ethical standards. Such an approach reflects the growing emphasis in Australian science on responsible research that balances discovery with conservation.

The dissection itself is a meticulous process. Careful incisions were made along the jawline and cheeks, exposing layers of muscle fibres responsible for chewing, facial movements, and communication. Each muscle was photographed and mapped, highlighting differences and similarities with other marsupials. This detailed anatomical record became a crucial reference point for interpreting the fossilised skull.

One of the challenges in such dissections is identifying muscle boundaries that can shift or overlap with age or health. The team relied on both classic anatomical guides and their own observations, noting the robust masseter muscles and orbicularis oris that give koalas their characteristic rounded faces. These findings not only clarified the fossil’s muscle attachment sites but also hinted at how ancient koalas may have adapted to their environment, perhaps having more mobile lips or nostrils for smell, communication or food handling.

By integrating modern anatomical data with fossil evidence, we were able to reconstruct the likely appearance and behaviour of the Pleistocene koala. This story highlights the creativity and care that go into unraveling Australia’s natural history.