While testing micro-CT scans for a wider project, paleontologist Matt Friedman was surprised to discover a highly detailed 319-million-year-old fish brain fossil.
“With all these features, I asked myself, ‘Is this really the brain I see?'” To tell Friedman at the University of Michigan.
“So we zoomed in on that area of the skull and did a second high resolution scan and it was very clear that that’s exactly what it should be. And this is a very obvious example. We decided just because there is, to take it further.”
Usually, the only vestiges of such ancient life remain are from the more easily preserved hard parts, such as animal bones, due to the rapid deterioration of soft tissues.
In the present case, however, a dense mineral, presumably pyrite, was infiltrated and replaced tissue that would have been preserved longer in a hypoxic environment. This allowed the scan to pick up what appeared to be details of the cranial nerves and soft tissue of the small fish. Cococephalus Wilde.
Scientists endangering invasive research methods, even though they have been in the hands of researchers since they were first described in 1925, because the ancient specimen is the only one of its kind. There was no such feature, so this feature remained hidden.
“Here we have seen remarkable preservation in fossils that have been examined several times previously by multiple people over the past century.” I will explain Friedman.
“But with these new tools for looking inside fossils, another layer of information is revealed.”
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This prehistoric estuarine fish may have hunted insects, small crustaceans, and cephalopods, chasing them with bony stick-supported fins called rays.
ray-finned fish, subclass actinopterygiimake up More than half of all living skeletal animals alive todayTuna, seahorse, etc. 96% of all fish.
This group split off from lobe-finned fish about 450 million years ago, some of which eventually became our own ancestors. C. Wild Then, about tens of millions of years ago, it followed a unique evolutionary path from a group of fish that are still alive today.
“Analysis puts this taxon outside the group that includes all fish species with living ray fins,” said University of Michigan paleontologist Rodrigo Figueroa and colleagues. . write in their paper.
“Brain structure details Cococephalus Thus, it influences the interpretation of neuronal morphology during early evolutionary stages of major vertebrate lineages. ”
Although some of the brain’s features are thought to have been lost during the decay and preservation process, the team was able to uncover certain morphological details. This suggests that the way this prehistoric forebrain developed is more similar to ours than the rest of living ray-finned fish alive today.
“Unlike all living fish with ray fins, fish brains Cococephalus Fold inward Note Friedman. “So this fossil captures a time before the characteristic feature of the ray-finned fish brain evolved. This provides us with some constraints on when this feature evolved.” This is something that didn’t work well before we had new data. Cococephalus.”
This inward fold is known as the forebrain exit. Just like us, two brain hemispheres surround a hollow space like the ‘c’ and their mirror images are joined. In contrast, the inverted forebrain found in still-living ray-finned fish instead has two bulging lobes with only a thin gap between them.
The researchers hope to scan other fish fossils in the museum’s collection to see what other signs of soft tissue may be hidden.
“The key conclusion is that the soft parts of this species are preservable and may be preserved in fossils that we have had for a long time. This has been known for over 100 years.” It’s a fossil.” To tell Friedman.
“That’s why preserving physical specimens is so important, because who knows what people will be able to do with the fossils in our collection in 100 years. .”
This research Nature.