A group of scientists found a unique fossil of a 380-million-year-old armadillo in Australia. The find is exceptional mainly because, in addition to the bones of the fish called gogo, internal organs including the heart, liver and stomach were also preserved. According to the scientists, the find also tells about human evolution.
Armadillos were fish-like vertebrates that grew to about nine meters. They were the first ever fish with jaws and teeth and ruled the earth for over 60 million years. They lived about 100 million years before the dinosaurs, yet these newly discovered organs prove that they were an important evolutionary link for most vertebrates, including humans, write the authors of the study on The Conversation server.
“We never knew anything about the soft organs of such old animals. Until now,” lead researcher Kate Trinajstic from Curtis University in Perth, Australia, told the BBC.
The new fossil proves that the organs in the body organized themselves and found their place much earlier than expected, adds the scientist.
“We all huddled around the computer and realized we had a heart. Basically, we couldn’t believe it! It was terribly exciting,” describes Trinajsticová. The entire scientific team is said to have realized at that moment that this was the greatest discovery of their lives.
For the first time in history, scientists now have the opportunity to study a heart that already resembles ours in many ways. It has a lower chamber and an upper atrium, although the human has two chambers and atria each.
However, the heart is much more complex than scientists thought in prehistoric fish. They believe this made the organ more efficient and played a key role in the evolution from a slow-swimming fish to a fast predator.
Another important finding is the position of the heart, which was located further forward than in primitive fish. The neck of the gogo fish was so short that its heart lay just behind the lower jaw. This created enough room for the later development of the lungs.
“Many of the things you see here are still in our bodies today, for example teeth and jaws. The front and back fins also appear for the first time, which gradually developed into arms and legs,” explains Zerina Johansonová, a world expert on armadillos from the National of the Natural History Museum in London, which, however, did not participate in the research.
The discovery fills important gaps in the understanding of evolutionary life on Earth, adds another independent expert, Martin Brazeau from London’s Imperial College. “It’s really exciting to see the result. The fish that my colleagues and I study are part of our evolution. This is part of the evolution of humans, animals that live on land, and fish in today’s waters,” he explains.
Discoveries of preserved bones tend to be relatively common, but preserved soft tissue is an absolute exception. The scientists had to proceed very carefully so as not to damage the organs in any way. For this, they used a modified X-ray, thanks to which some fish could even see what they had last eaten. They could also create a 3D model of the heart and other organs, which is even rarer.
Thanks to this, the researchers were also able to estimate the exact size of the organs and discovered, for example, that the gogo used its relatively large livers as floats – similar to how today’s sharks do.
In the Kimberley region of Australia, near the Gogo reefs, after which this fish takes its name, a unique combination of minerals is found that also preserves the internal organs. The heart is 250 million years older than the last oldest vertebrate heart discovered.