Ancient fish bones reveal clues about the evolution of eating

Long before the first mammals walked the Earth, the oceans were home to strange, powerful fish. Some of these ancient fish eventually crawled onto land and kicked off a new chapter in evolution.

Now, thanks to new fossil research, we’re learning even more about how these early animals lived – and ate.

In a new study led by scientists from Flinders University, researchers examined jawbones from 380-million-year-old lungfish found in Western Australia’s remote Gogo fossil field.

The findings shed light on the evolution of feeding strategies in fish that are closely related to all land-dwelling vertebrates, including us.

Biting power of ancient fish

The researchers used 3D finite element modeling (FEM) – a tool more commonly seen in engineering. They digitally tested how different fossilized jaws handled biting stress.

By running simulations on fish jawbones from multiple species, the team revealed surprising variation in shape, strength, and eating behavior.

“Lungfish are ‘sister taxa’ to the tetrapods – or all four-limbed animals with a backbone, including humans – which means they are our closest ‘fishy’ relatives,” noted Dr. Alice Clement.

“They have an extensive fossil history stretching back over 400 million years and still with living representatives today and their phylogenetic proximity to tetrapods giving insight into our long-distant ancestors who first made the move from water to land.”

That close relationship makes lungfish fossils especially valuable. The Gogo Formation in northern Western Australia is a goldmine of such specimens. With 11 known species, it holds the most diverse group of lungfish ever discovered from one place or time.

Fish bite force and eating style

Until now, scientists knew these fish had different jaw shapes. What they didn’t know was how those jaws worked. The new models changed that.

“We’re slowly teasing apart the details of how the bodies and lifestyles of these animals changed, as they moved from being fish that lived in water, to becoming tetrapods that moved about on land,” said Dr. Clement.

By scanning seven fossil species and applying FEM to five of them, the team was able to measure how the jawbones responded to stress during simulated bites.

Fossil bites defy expectations

The dataset is the most detailed look yet at biting performance in any fossil fish. It provides biomechanical evidence for diverse feeding adaptations and niche partitioning within Gogo lungfishes, noted Dr. Olga Panagiotopoulou, a functional anatomist at Touro University California.

Some of the findings contradicted assumptions. Jaws that looked sturdy on the outside didn’t always perform well in bite-force simulations. And some that looked more delicate turned out to be much stronger than expected.

“The results were somewhat surprising, with some ‘robust’-looking lower jaws appearing to not be all that well suited to biting stress, and some of the more gracile or slender jaws appeared to be able to withstand stress and strain very well,” said Professor John Long of Flinders University.

“This diversity of biomechanical function seen in the Gogo lungfishes suggest that there was niche partitioning and trophic differentiation among lungfishes, possibly accounting for their incredibly high species diversity at this site.”

When fish reinvented eating

The Devonian period, often called the “Age of Fishes,” was ruled by placoderms and other ancient species for about 60 million years. Many of their fossils were found decades ago, but new tools like FEM are finally revealing how these animals actually lived.

Joshua Bland, a researcher at the Flinders Palaeontology Lab, is the study’s lead author. He noted that the Gogo lungfish of the Late Devonian reefs were truly unique, with species possessing a host of different behaviors and abilities.

“To capture parts of that story, hidden in the bone, was extremely rewarding. It felt like we lifted the veil on some real functions behind the form. It was impressive to see the more complex morphology perform better in our tests,” said Bland.

Future science from old bones

All 3D models from the study are now available on Morphosource, allowing other researchers to explore and expand on this work.

By combining old fossils with new technology, the team has brought us one step closer to understanding the creatures that helped shape life on land.

The researchers have also shown that even after 380 million years, ancient bones can still have something new to say.

The full study was published in the journal iScience.

Image Credit: John Long, Flinders University

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