Paleontologists Stumble Across 15-Million-Year-Old Fish Fossils That Are So Well Preserved, Their Last Meals Are Intact
Discovered in Australia, the fossils represent a new species that lived during the Miocene epoch and highlight how iron-rich rock can protect specimens over time
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Fossilized fish found in Australia are so well preserved that paleontologists can see what the creatures ate for their last meals roughly 15 million years ago.
They described the fish—which belong to a newly identified species called Ferruaspis brocksi—in a paper published Monday in the Journal of Vertebrate Paleontology.
F. brocksi was a small fish that lived in freshwater lakes in what is now central New South Wales, the state in southeast Australia. Today, central New South Wales is mostly arid farmland. But, when the fish were alive during the Miocene epoch, the region was a lush, temperate rainforest.
Paleontologists stumbled upon several intact F. brocksi fossils while exploring a research site known as McGraths Flat near the town of Gulgong. After coming up empty at a nearby fossil site, they headed over to McGraths Flat to see if they would have better luck there—and, as it turned out, they did.
Once the team arrived, Jochen Brocks, an earth scientist at the Australian National University, decided to split open a rock. He was shocked to find a nearly perfect fossilized fish inside, complete with soft tissue and an articulated skeleton, which means the bones were still arranged as they were during the fish’s life. But he and his colleagues didn’t recognize the creature.
The researchers kept looking and found a few dozen additional fossils of the same type of fish at the site. They were so well-preserved that the researchers could see the animals had eaten phantom midge larvae, insects and bivalves before they died; one also had a parasite stuck to its tail, a juvenile freshwater mussel known as a glochidium.
“It was a complete fluke,” Jochen tells the Australian Broadcasting Corporation’s Ellen Phiddian and Peter de Kruijff. “Just because we had nothing else to do, we looked at those rocks.”
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The fossilized fish also surprised the paleontologists, because they were entombed in a mineral known as goethite, which contains lots of iron. They didn’t realize such an iron-rich mineral could preserve fossils so well—so, the discovery may inspire paleontologists to take a closer look at goethite rocks in the future.
The mineral also inspired part of the new species’ scientific name, Ferruaspis brocksi. “Ferru” stems from the Latin word for iron, while “brocksi” is a nod to Brocks, who discovered the fossils.
“We tend not to think of iron-rich rocks as containing great fossils, so the fact that they’ve recovered it opens up a new area for people to investigate,” says Kate Trinajstic, a paleontologist at Australia’s Curtin University who wasn’t involved with the research, to the Australian Broadcasting Corporation.
When scientists brought the fossilized fish back to the lab, they put them under a scanning electron microscope. The technology revealed the remnants of cells called melanosomes, which produce the pigment melanin. These cells indicate that F. brocksi had two lateral stripes on its side, a light-colored stomach and a darker-colored back.
Paleontologists have used fossilized melanosomes to deduce the color of bird feathers. But this marks the first time they have been used to reconstruct the color pattern of a long-extinct fish, according to a statement from the Australian Museum.
F. brocksi belongs to the Osmeriformes order, a group of ray-finned freshwater fish that includes the Australian grayling and the Australian smelt. But until now, scientists had never discovered a fossilized Osmeriformes fish in the country, which made it difficult to determine when the creatures first arrived in Australia and how they’ve evolved over time.
Now, the team hopes the fossilized remains of F. brocksi may shed some light on the Osmeriformes group’s history and lineage. It may also help them understand Australia’s ancient ecosystems during the Miocene, when the continent’s climate was shifting.
“At the time these fish died and were preserved, that was a transitional period for Australia,” says study co-author Michael Frese, a virologist at the University of Canberra in Australia, to the Guardian’s Petra Stock. “Basically, it’s a history lesson, or a geological lesson, of what happens if the climate changes fundamentally.”
