Biology

Oldest known heart found preserved in 380-million-year-old fish fossil

Oldest known heart found preserved in 380-million-year-old fish fossil
A museum display model of the ancient fish, fossils of which have been found to contain the oldest preserved heart of any vertebrate
A museum display model of the ancient fish, fossils of which have been found to contain the oldest preserved heart of any vertebrate
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A museum display model of the ancient fish, fossils of which have been found to contain the oldest preserved heart of any vertebrate
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A museum display model of the ancient fish, fossils of which have been found to contain the oldest preserved heart of any vertebrate
The fossil, encased in limestone, which includes the preserved heart still inside
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The fossil, encased in limestone, which includes the preserved heart still inside
Professor Kate Trinajstic inspects the fossils
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Professor Kate Trinajstic inspects the fossils
The fossil stomach of the ancient fish
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The fossil stomach of the ancient fish
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Soft tissues don’t fossilize well, so most of the time scientists have to infer organ anatomy from just bones. But an unexpected treasure trove of new information has been discovered in Australia, with a 380-million-year-old fish fossil preserving the oldest heart ever found.

The fossil belongs to a species of arthrodire, a group of armored fish that ruled the oceans during the Devonian period between about 420 and 360 million years ago. These were some of the first vertebrates to evolve jaws, which was a pretty major innovation. But the path of organ evolution is much harder to trace – until this specimen came along.

Discovered in the Gogo Formation, the remains of an ancient reef system in northwestern Australia, the fossil captures the heart, stomach, intestines and liver of the ancient fish. Better yet, they’re preserved in their original positions in three dimensions, rather than being squashed flat by heavy rock over millions of years, as is usually the case.

The fossil, encased in limestone, which includes the preserved heart still inside
The fossil, encased in limestone, which includes the preserved heart still inside

The specimens are still encased in limestone, so the scientists used neutron beams and synchrotron X-rays to image them. From this the team could see the shape and structure of the organs with unprecedented precision, revealing a surprisingly advanced anatomy for their age. This also allowed the team to construct the first 3D model of the heart of an arthrodire, consisting of an S shape with two chambers stacked on top of each other.

"For the first time, we can see all the organs together in a primitive jawed fish, and we were especially surprised to learn that they were not so different from us," said Professor Kate Trinajstic, lead researcher on the study. "Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a larger leap between jawless and jawed vertebrates. These fish literally have their hearts in their mouths and under their gills – just like sharks today.”

The team also found that the fish’s liver was large and would have helped with its buoyancy – another shark-like trait. There was no sign of lungs though, which indicates they evolved in later groups and weren’t as ancestral as some hypotheses propose.

The research was published in the journal Science. A 3D animation of the scanned organs can be seen in the video below.

3D scan of the oldest heart ever found

Source: Curtin University

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2 comments
2 comments
Nelson Hyde Chick
I wonder who or what will be analyzing fossils of use millions of years from now after we had long ago destroyed the Earth?
Cassio Ribeiro Muylaert
Bom dia.Parabens e muito obrigado pelo artigo sobre Peixe primitivo com coração preservado como Fossil.Muito interessante para compreender a Evolução dos peixes .Att