this fossil could rewrite what we know about the past!

A group of researchers led by Curtin University in Australia discovered a 380 million year old heart, the oldest ever found, as well as a fossilized stomach, intestine and liver from an ancient jawed fish called Arthrodira, which sheds new light on the evolution of our own bodies.

This discovery of mineralized organs, including a perfectly preserved heart, makes the Arthrodira de Gogo (Gogo Formation) – a mineral site in Western Australia exhibiting exceptional preservation of a Devonian reef community – the world’s finest jawed vertebrates understood by science to date. It also illuminates an evolutionary transition in the lineage of living jawed vertebrates, which includes mammals and humans.

A Devonian heart

This research revealed that the position of organs in the bodies of Arthrodira, an extinct class of armored fish that flourished during the Devonian, a period spanning from 419.2 million years ago to about 358.9 million years ago, is similar to that of modern sharks. Anatomically, this provides new essential evolutionary avenues, impacting a variety of organisms, including humans.

According to research director Professor Kate Trinajstic, This discovery is remarkable because the soft tissues of ancient species are rarely preserved, and it is even rarer to find 3D preservation. Experts point out that most cases of soft tissue preservation are seen in flattened fossils, where the soft anatomy almost resembles a bubble in the rock.

In addition to the specific conditions of this discovery, modern scanning techniques have been crucial in allowing the study of these fragile soft tissues without destroying them. Experts believe that a few decades ago, such a project would have been impossible. Furthermore, paleontologists have emphasized that, although evolution is often seen as a series of small steps, This type of fossil suggests that there was a big jump from jawless to jawed vertebrates.

These fish had their hearts located near the mouth and under the gills, just like modern sharks. Additionally, the discovery provides the first 3D model of a complex S-shaped heart in an Arthrodira, consisting of two chambers.

According to a press release, these characteristics developed in these early vertebrates, providing a unique opportunity to understand how the head and neck region began to evolve to accommodate the jaws, a crucial step in the evolution of our own bodies.

We are not so different from this fossil

However, upon observing all the organs together in a primitive jawed fish for the first time, experts were surprised to find that they were not so different from ours. Despite this, they identified a fundamental difference: the large liver allowed the fish to float, just like sharks do today.

Furthermore, some contemporary fish have lungs that evolved from swim bladders, but until now, no evidence of lungs has been found in extinct armored fish. The new information suggests that lungs evolved independently in bony fish at a later date.

Thus, by discovering the only known example of a three-dimensionally mineralized heart, a thick-walled stomach and a liver in an Arthrodira in the Upper Devonian Gogo Formation, scientists have uncovered the first phylogenetic evidence for the repositioning of the heart at this time, in connection with the evolution of the complex neck region in jawed vertebrates.

Finally, the application of synchrotron and neutron microtomography to this material reveals evidence of a heart clearly separated from the liver and other abdominal organs, as well as the absence of lungs. According to scientists, the knowledge gained will be crucial for making connections with future discoveries, allowing a more precise understanding of the evolutionary chain that led to the living beings we know today.

Article reference:

Trinajstic K., Long J., Sanchez S., et al. Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte. Science (2022).