First Fossilized Heart Of Prehistoric Animal Discovered

In a breakthrough discovery, a perfectly preserved 3-D fossilized heart was found in an 113-119-million-year-old fish from Brazil called Rhacolepis, according to a report published in the journal eLife. The findings will help researchers observe the anatomy of an extinct group of fish and consequently understand the evolution of the first backboned animals as well as the development of the heart.

For the past decades, the fossil remains of vertebrates, or backboned animals, were studied mainly from their fossilized footprints or bones. It was believed that finding a well-preserved soft tissue in ancient fossils is impossible. Therefore, finding an absolutely intact fossilized heart in a 120-million-year-old prehistoric animal was a major discovery for researchers.

The new discovery was made by imaging a fossil concretized within limestone by applying synchrotron X-ray tomography down to 6µm sections.  The heart was then extracted part by part using software to digitally restore its features. The widely popular method is being used in paleontology for the past decade to understand the complex soft-tissue structures in fossils.

The discovery of the fossilized Rhacolepis heart is important as it shows the valve condition present in an ancient member of the ray-finned fish group. The heart pattern seen in the Rhacolepis represents a good intermediate condition between the most primitive and most advanced type, and simple patterns often have more complex and hidden meanings encapsulated in them.

"The discovery of complete soft tissues preserved as whole internal organs in a fossil was a bit of a Holy Grail for paleontologists, " said John Long, a paleontology professor at Flinders University, Australia in a recent article in The Conversation. "Such discoveries could contribute to understanding deeper evolutionary patterns as internal soft organs have their own set of specialized features." The find also indicates the immense possibilities of more discoveries of this kind in the future.