Paleontologists Discover World’s Oldest Intact Fossilized Heart Ever Found

by Lauren Boisvert
(Image Credit: Arctic Images/Getty Images)

In September, paleontologists found the oldest fossilized heart from a prehistoric fish in Australia. It’s the oldest three-dimensionally preserved heart ever discovered at 380 million years old. It is already difficult to find fossilized soft tissue because usually it erodes and rots away before fossilization. But this is an extraordinary find. The paleontologists published their discovery in Science last month.

John Long, a paleontologist at Flinders University in Australia and co-author of the paper, told BBC News that this was “a mind-boggling, jaw-dropping discovery.” He explained, “We have never known anything about the soft organs of animals this old, until now.” 

According to the study, there were also livers, stomachs, and intestines preserved alongside the heart. These specimens came from placoderms. These are armored fish that researchers consider “our earliest jawed ancestors,” said Kate Trinajstic. She is the lead author of the study and a paleontologist at Curtin University in Australia. According to Smithsonian Magazine, placoderms lived 416 million to 359 million years ago. 

Paleontologists found the fossils in the Gogo Formation of Western Australia. The limestone in the formation preserved these soft tissues. Researchers also found fish muscles and embryos there in the past. Using neutron beams and synchrotron X-rays, researchers scanned the fossils in the formation. They found striking similarities to sharks and, surprisingly, humans.

“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 Trinajstic. “However, there was one critical difference—the liver was large and enabled the fish to remain buoyant, just like sharks today.”

Paleontologists Find Prehistoric Heart Fossil from 380-Million-Year-Old Fish

Researchers determined that the placoderms may have evolved independent lungs later on, in comparison to lungfish and bichirs of today which evolved lungs from swim bladders. The placoderm fossils didn’t show any evidence of having lungs, which led paleontologists to the later-evolution theory.

As for the hearts, they are two-chambered and S-shaped, located under the gills. Trinajstic told the Australian Associated Press that the presence of a two-chambered heart in such an early prehistoric fish was surprising.

“Here we are, right at the beginning of the jawed vertebrates, and that step’s already there,” she said. According to Trinajstic, these fish were fast-moving predators, and the two-chambered hearts were most likely more efficient.

Everywhere, experts and fellow paleontologists are celebrating the success of the incredible find. Placoderm expert Zerina Johanson of London’s Natural History Museum wasn’t involved in the study, but lauded the researchers’ discovery. “There are many things going on in these placoderms that we see evolving to ourselves today such as the neck, the shape and arrangement of the heart and its position in the body,” she told the BBC.

José Xavier Neto, who was part of a 2016 group that discovered the first-ever fossilized vertebrate heart, also shared words of celebration and excitement. “Only six years after our initial discovery,” he said, “it’s great to see that other groups are also being able to report on fossil hearts. The field is really new, and we really need high-quality data.”