An international team of researchers has discovered in Australia a 380-million-year-old heart, the oldest ever found, along with a fossilized stomach, intestine and liver in an ancient jawed fish. The incredible finding, released in the journal ‘Science’, sheds light on the evolution of our own body.
The fossils were found embedded in the limestones of the Gogo Formation in the Kimberley region of Western Australia, originally a large reef. For the researchers, this is a remarkable discovery, given that the soft tissues of ancient species are rarely preserved, least of all in three dimensions like these.
The fossils belong to an extinct class of armored fish. His study with neutron beams and synchrotron X-rays surprised paleontologists, since the anatomy of Gogo’s fish was surprisingly surprising. similar to that of the modern sharkoffering vital new evolutionary clues.
heart in mouth
“Evolution is often thought of as a series of small steps, but these ancient fossils suggest that 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,” says Kate Trinajstic, from the School of Molecular Sciences at Curtin University in Perth.
The heart is S-shaped and made up of two chambers, with the smaller chamber sitting on top. Trinajstic believes that these features developed in these early vertebrates, offering a unique window into how the head and neck region began to change to fit jawsa critical stage in the evolution of our own bodies.
illustration of a gogo fish
“For the first time, we can see all the organs together in an early jawed fish, and we were especially surprised to learn that they weren’t that different from us,” he says.
However, there was one critical difference: the liver was large and allowed the fish to float, much like sharks do today. “Some of the extant bony fishes, such as lungfishes and birches, have lungs that evolved from swim bladders, but it was significant that we found no evidence of lungs in any of the extinct armored fishes we examined, suggesting that they evolved independently in bony fish at a later time,” says the researcher.
A paleontologist’s dream
“These new discoveries of soft organs in these ancient fish are truly a paleontologist’s dream, because these fossils are undoubtedly the best preserved in the world for this time,” says John Long of Flinders University and co-author of the study.
For Per Ahlberg, a professor at Uppsala University and also a co-author of the study, “what is really exceptional about Gogo fish is that their soft tissues are preserved in three dimensions. Most cases of soft tissue preservation are found in flattened fossils, where the soft anatomy is little more than a speck in the rock. We are also very fortunate 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.”