380 million year old fossilized heart discovered in WA
September 16, 2022
Image Credit: Courtesy of Curtin University
The preserved liver, stomach, intestine and heart of the fossilized prehistoric jawfish, the Arthrodire placoderm, are the oldest ever found.
Paleontologists from Curtin University have discovered the 380 million year old fossilized organs of the prehistoric jawed fish Placoderm Arthrodire. The preserved liver, stomach, intestine and heart – the oldest ever found – were discovered in the Gogo Formation, which is a lagerstätte (a German term that refers to a sedimentary deposit that features extraordinary fossils with exceptional preservation, sometimes including preserved soft tissue) in the Kimberley region of Western Australia.
The specimens, which are still embedded in limestone concretions, were scanned with neutron beams and synchrotron X-rays, allowing researchers to construct 3D images of soft tissue organs without destroying them.
“For the first time we can see all the organs together in a primitive jawed fish,” said Professor Kate Trinajstic, senior researcher at Curtin University’s School of Molecular and Life Sciences and Western Australian Museum. “These fish literally have their hearts in their mouths and under their gills, just like sharks today.”
The prehistoric fish had an intricate S-shaped heart consisting of two chambers, with the smaller one sitting on top. According to Professor Trinajstic, these features have been advanced in these early vertebrates, offering insight into how the neck and head region evolved over time to accommodate the jaws.
“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,” she says.
The arthrodire’s liver also provides a window into its evolutionary past. Like modern sharks, the prehistoric fish’s large liver allowed it to maintain buoyancy.
“Some of today’s bony fish, such as lungfish and birches, have lungs that evolved from the swim bladder,” Kate explains. “We found no evidence of lungs in any of the extinct armored fishes we examined, suggesting that they independently evolved into bony fishes at a later date.”
The extinct armor-jawed fishes lived during the Devonian period (419 to 359 million years ago).