Can 380-million-year-old fossilized organs last into the present? A new discovery suggests they can…
Paleontologists can now view prehistory in ways previously unimaginable thanks to advances in technology.
Look no further than a new study of a 380-million-year-old fossilised fish from Australia's Devonian Period. The study, published on September 15th by a research team led by palaeontologist Kate Trinajstic, used x-ray and neutron beams to peer inside the remains of a Gogo fish, a member of the placoderms, an extinct lineage of armoured fishes. What they discovered was incredible: not only were its organs intact, but they were also preserved in three dimensions.
(A 380-million-year-old fossilized heart.)
The most spectacular feature preserved in the fossil was the Gogo's heart. It was discovered to be near the base of the jaw, S-shaped, with two chambers, and vertically oriented, according to the researchers. The two-chambered heart may appear primitive in comparison to the four-chambered hearts of bony fishes, but it may have aided efficiency. While the hearts of more primitive vertebrates, such as Lampreys, have three horizontal chambers, the Gogo's vertical heart allowed for more active behaviours in Devonian seas.
The heart was not the only organ discovered in the Gogo Fish. The liver, intestines, and stomach were all saved as well. The liver had two lobes and was proportionately large, which researchers believe helped buoyancy, similar to sharks. The stomach had thick and muscular walls, implying that it digested food with stomach acids. Paleontologists were surprised by how developed these traits were given the age of the fossil, which may indicate that advanced internal systems first appeared in vertebrates.
Placoderms such as the Gogo Fish represent an intriguing lineage in Earth's history. They were vertebrates with developed jaws, making them more derived than animals like lampreys and hagfish. These jaws differed from those of ray-finned and cartilaginous fishes in that they were made up of numerous plates that worked together to provide strong bite forces to placoderms. Another distinction between placoderms and ray-finned fishes was the absence of lungs.
We can see evidence of this absence in our Gogo Fish. While the Gogo's organs have been meticulously preserved, the lungs are noticeably absent. This isn't a strange coincidence or a new discovery; palaeontologists believe lungs evolved in bony fishes after they split from placoderms[viii]. The Gogo's lack of lungs may confirm this, explaining why placoderms struggled at the end of the Devonian while bony fish thrived. Sharks, on the other hand, lack lungs and were present in the Devonian, so maybe not...
The Gogo Fish
The presence of organs in any fossil is astonishing. It is groundbreaking to discover them on a 380-million-year-old specimen. The internal anatomy of the Gogo Fish demonstrates that early vertebrates already had advanced organs and that lungs are not ancestral to jawed fishes. As the use of technology spreads throughout palaeontology, discoveries like this will only become more common.
Thank you for taking the time to read today's article! If you're interested in animals like placoderms, I recommend reading about and visiting the Royal Ontario Museum's Dawn of Life Exhibit. Dawn of Life is a must-see exhibit about life before the dinosaurs, with beautiful art, stunning centrepieces, and more fossils than you can handle!
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