Discovery of a remarkable 380 million year old core – Shedding new light on evolution

The Gogo fish fossil where the 380 million year old 3D preserved heart has been discovered by researchers. Photographed at the WA Museum. Credit: Yasmine Phillips, Curtin University

Paleontologists have discovered a 380 million year old heart – the oldest ever found – alongside a separate fossilized liver, stomach and intestine in an ancient jawed fish, shedding new light on the evolution of our own body.

Vital new evolutionary clues are provided by research, which has revealed that the position of organs in the body of arthrodires is similar to modern shark anatomy. Arthrodires are an extinct class of armored fish that flourished during the Devonian period from 419.2 million years ago to 358.9 million years ago. The study was published on September 15, 2022 in the journal Science.

It was a remarkable finding given that the soft tissues of ancient species were rarely preserved and it was even rarer to find 3D preservation, said lead researcher John Curtin, Professor Emeritus Kate Trinajstic, of Curtin’s School. of Molecular and Life Sciences and the Western Australian Museum.

Preserved stomach of a Gogo fish fossil

The preserved stomach of a Gogo fish fossil under the microscope. Photographed at the WA Museum. Credit: Yasmine Phillips, Curtin University

“As a paleontologist who has studied fossils for over 20 years, I was truly amazed to find a beautifully preserved, 3D heart in a 380 million year old ancestor,” Prof Trinajstic said.

“Evolution is often thought of as a series of small steps, but these ancient fossils suggest there was a bigger jump between jawless and jawed vertebrates. These fish literally have their hearts in their mouths and under their gills, just like sharks today.”

This research presents – for the very first time – the 3D model of a complex S-shaped heart in an arthrodire composed of two chambers, the smaller one being located above.

Animation of heart position created by Alice Clement.

Professor Trinajstic said these features were advanced in these early vertebrates. This provides a unique window into how the head and neck region began to change to accommodate the jaws, which was a critical step in the evolution of our own bodies.

Gogo Fish Diorama

Gogo fish diorama at the WA Museum Boola Bardip. Credit: Professor Kate Trinajstic, Curtin University

“For the first time we can see all the organs together in a primitive jawed fish, and we were particularly surprised to learn that they weren’t so different from us,” Prof Trinajstic said.

“However, there was one key difference – the liver was large and allowed the fish to stay buoyant, much like sharks today. Some of today’s bony fish, such as lungfish and bichirs, have lungs that evolved from swimbladders, but it is significant that we found no evidence of lungs in any of the extinct armored fish we examined, suggesting that they evolved independently in bony fish at a given time. later date.”

The fossils were collected from the Gogo Formation, located in the Kimberley region of Western Australia. It was originally a large reef.

The researchers used neutron beams and synchrotron X-rays to scan the specimens, still embedded in the calcareous concretions, and constructed three-dimensional images of the soft tissues inside based on the different densities of minerals deposited by bacteria and the surrounding rock matrix. To do this, they enlisted the help of scientists from Australia’s Nuclear Science and Technology Organization in Sydney and the European Synchrotron Radiation Facility in France.

In addition to previous muscle and embryo discoveries, this new discovery of mineralized organs makes Gogo arthrodires the best understood of all jawed stem vertebrates and clarifies an evolutionary transition down the line to living jawed vertebrates, which includes mammals and humans.

Professor Kate Trinajstic inspects ancient fossils

Curtin University professor Kate Trinajstic inspects ancient fossils in the WA Museum. Credit: Adelinah Razali, Curtin University

“These new discoveries of soft organs in these ancient fish are truly the stuff of paleontologists’ dreams, because without a doubt, these fossils are the best preserved in the world for this age,” said co-author Professor John Long of[{” attribute=””>Flinders University. “They show the value of the Gogo fossils for understanding the big steps in our distant evolution. Gogo has given us world firsts, from the origins of sex to the oldest vertebrate heart, and is now one of the most significant fossil sites in the world. It’s time the site was seriously considered for world heritage status.”

“What’s really exceptional about the Gogo fishes is that their soft tissues are preserved in three dimensions,” said co-author Professor Per Ahlberg, from Uppsala University. “ Most cases of soft-tissue preservation are found in flattened fossils, where the soft anatomy is little more than a stain on the rock. We are also very fortunate in that modern scanning techniques allow us to study these fragile soft tissues without destroying them. A couple of decades ago, the project would have been impossible.”

Reference: “Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte” by Kate Trinajstic, John A. Long, Sophie Sanchez, Catherine A. Boisvert, Daniel Snitting, Paul Tafforeau, Vincent Dupret, Alice M. Clement, Peter D. Currie, Brett Roelofs, Joseph J. Bevitt, Michael S. Y. Lee and Per E. Ahlberg, 15 September 2022, Science.
DOI: 10.1126/science.abf3289

The Curtin-led research was a collaboration with Flinders University, the Western Australian Museum, the European Synchrotron Radiation Facility in France, the Australian Centre for Neutron Scattering at Australia’s Nuclear Science and Technology Organisation, Uppsala University, Monash University’s Australian Regenerative Medicine Institute and the South Australian Museum.

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