What would you eat for lunch, if you knew someone was going to be judging you for it 15 million years later?

That was certainly not the thought of a little freshwater fish that was swimming in what is now known as the McGraths Flat fossil site near Gulgong in New South Wales, Australia.

And yet, thanks to its fossilized remains – uncovered recently by a team of scientists from the Australian Museum and the University of New South Wales, Sydney – we now have a rare insight into what exactly this little fish ate.

What’s more, the incredible preservation of this fish also shows the patterning and colors of its scales.

In the research paper, which was recently published in The Journal of Vertebrate Palaeontology, this new species of fish from the Osmeriformes group, which has been named the Ferruaspis brocksi.

As the paper’s lead author, Dr Matthew McCurry explained in a statement, this perfectly preserved fossil is proving extremely important for Australian paleontology, since it helps to piece together a missing chunk of history:

“The discovery of the 15 million-year-old freshwater fish fossil offers us an unprecedented opportunity to understand Australia’s ancient ecosystems and the evolution of its fish species, specifically the Osmeriformes group during the Miocene epoch, 11-15 million years ago.”

With the discovery of this little fish fossil, some of these missing bits of knowledge can finally be pieced together.

Found preserved in iron-rich rock, this fish specimen is particularly striking thanks to the incredible preservation of its characteristics, giving a clear indication as to how fish looked and lived back during the Middle Miocene Epoch.

This is not unusual at the McGraths Flat site, a former temperate rainforest in which a significant number of fossils – including fish, insects, plants, and pollen – have been found to have been preserved in excellent detail.

And that is absolutely the case with this fish, as McCurry continued:

“Not only does this fossil provide a unique snapshot into the environment it lived in the Central Tablelands, but also because its stomach contents are so well preserved it allows us a glimpse into the behaviour of these ancient species. We now know that they fed on a range of invertebrates, but the most common prey was small phantom midge larvae.”

Though this tells us a lot about the fish itself, we also garner knew knowledge about the abundance of midge larvae in the ecosystem, offering a deeper look into how the Australian rainforest was populated at the time.

Moreover, the understanding of this particular fish is crucial to experts’ knowledge of some of Australia’s unique ecology and ecosystems – in particular, how they have adapted developed to make Australian nature so strikingly different to species found elsewhere:

Osmeriformes are a diverse group of fish within Australia which includes species like the Australian Grayling and the Australian Smelt. But, without fossils it has been hard for us to tell exactly when the group arrived in Australia and whether they changed at all through time.”

Though it was an extremely long time ago, our understandings of the adaptations of Australia’s ecology and habitats over time is crucial, especially as we face some of the planet’s biggest challenges yet.

Only with a deep understanding of how these creatures, their ancestors, and their homes have evolved, can we protect them from possible threats into the future.

And by lying fossilized in the rock for 15 million years, this little fish is crucial to this plight.

If you thought that was interesting, you might like to read about why we should be worried about the leak in the bottom of the ocean.