(ORDO NEWS) — An ancient fossil of one of the earliest vertebrates on our planet holds a breathtaking surprise.
Inside a 380-million-year-old fossilized shellfish, paleontologists have discovered a mineralized heart that is exceptionally well-preserved in three dimensions.
This is an incredible find. Soft tissues are rare in the fossil record and tend to decompose before fossilization can occur. Even rarer are three-dimensional soft tissues.
Scanning the fossil allowed scientists to study its anatomy in 3D without having to break the precious object apart.
Thanks to the amazing state of preservation in the fossil, details such as the atrium, ventricle, and excretory tract can be clearly identified.
The heart of an ancient fish was an S-shaped organ consisting of two chambers, with the smaller chamber located on top of the larger one.
The researchers say this was much more advanced than paleontologists thought, and could provide important information about the evolution of the head and neck region and how they changed to accommodate the jaws.
“As a paleontologist who has been studying fossils for over 20 years, I was truly amazed to find a beautifully preserved three-dimensional heart in a 380-million-year-old ancestor,” said Kate Trinaistik of Curtin University in Australia.
“Evolution is often presented as a series of small steps, but these ancient fossils suggest that there was a big leap between jawless and jawed vertebrates. The heart of these fish is literally in the mouth and under the gills – just like modern sharks.
Where they found a valuable heart
The fossil comes from a location known as the Gogo Formation, in the northernmost corner of Western Australia.
During the Devonian, between 419.2 million years ago and 358.9 million years ago, this region was a vast reef where life flourished. It is now a fossil bed classified as a Lagerstätte – so exceptional that sometimes even soft tissue is preserved.
The fossil was left behind by an animal from an extinct class of armored fish called arthrodires. These creatures flourished for about 50 million years during the Devonian period before disappearing during a major global extinction near the end of the period.
Consisting of a rough chunk of limestone adorned with a scattering of strange biological features, the specimen would once have been difficult to analyze without risking destruction.
Luckily, we no longer have to open fossils to see what’s inside.
“What is really exceptional about gogo fish is that their soft tissues are preserved in three dimensions,” said paleontologist Per Ahlberg from Uppsala University in Sweden.
“Most cases of soft tissue preservation are found in oblate fossils, where the soft anatomy is nothing more than a stain on the stone.
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, this project would have been impossible.”
How rare fossils are studied
With the help of scientists from the Australian Organization for Nuclear Science and Technology and the European Synchrotron Radiation Center in France, the team used neutron beams and synchrotron X-ray imaging to map the varying densities of minerals within the fossil.
These densities revealed not only the preserved arthrodire bones, but also other less durable features a spectacular heart, as well as a stomach, intestines, and liver.
The presence of other organs allowed the team to study the anatomical structure of the fish.
“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.
However, there was one important difference – the liver was large and allowed the fish to stay afloat, like today’s sharks. no evidence of lungs in any of the extinct armored fish we studied, suggesting that they evolved independently in teleosts at a later time,” the scientists write.
Previously discovered fossil specimens from the Gogo Formation have allowed paleontologists to reconstruct and understand the musculature of the Gogo arthrodires.
In addition, arthrodire embryos were found in the formation. The new pattern suggests there may be even more treasures in the Australian outback just waiting to be discovered.
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