(ORDO NEWS) — Researchers have discovered a 380-million-year-old heart – the oldest ever found – along with separate fossilized stomachs, intestines and livers from an ancient jawed fish, shedding new light on the evolution of our own bodies.
A new study published today in the journal Science shows that the position of the organs in the body of arthrodyres – an extinct class of armored fish that flourished during the Devonian period from 419.2 million years ago to 358.9 million years ago – is similar to the position of the organs of a modern shark. . This offers scientists vital new evolutionary clues.
Lead researcher, John Curtin, Professor Emeritus Keith Trinaistik of the Curtin School of Molecular and Life Sciences and the Western Australia Museum, said the discovery was remarkable given that the soft tissues of ancient species were rarely preserved, and even rarer to find three-dimensional preservation.
“As a paleontologist who has been studying fossils for over 20 years, I was genuinely amazed to find a beautifully preserved three-dimensional heart in a 380-million-year-old ancestor,” says Prof Trinaistik.
“Evolution is often presented as a series of small steps, but these ancient fossils suggest that there was a big leap between jawless and jawed vertebrates.
The heart of these fish is literally in the mouth and under the gills – just like modern sharks.
This study presents the first 3D model of a complex S-shaped heart in a two-chamber arthrodire, with the smaller chamber on top.
Professor Trinajstick said these traits were developed in such early vertebrates, offering a unique window into how the head and neck region began to change to accommodate the jaws, a critical stage in the evolution of our own bodies.
“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 Prof Trinaistik.
“However, there was one important difference – the liver was large and allowed the fish to stay afloat, like today’s sharks.
No evidence of lungs in any of the extinct armored fish we have studied, suggesting that they evolved independently in teleosts at a later time.”
Enlisting the help of scientists from the Australian Organization for Nuclear Science and Technology in Sydney and the European Synchrotron Radiation Facility in France, the researchers used neutron beams and synchrotron X-rays to scan samples still in limestone nodules and built 3D images of the soft tissue inside them based on various density of minerals deposited by bacteria and surrounding rock.
This new discovery of mineralized organs, in addition to previous finds of muscles and embryos, makes the Gogo arthropod the most studied of all jawed vertebrates and clarifies the evolutionary lineage to living jawed vertebrates, including mammals and humans.
Scientists note that new discoveries of soft organs in these ancient fish are the stuff of paleontologists’ dreams, since, without a doubt, these fossils are the best preserved in the world for this era. They show the value of fossils in understanding the great steps in distant evolution and provide an opportunity to make new world discoveries.
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