Scientists stumbled upon the oldest brain of any vertebrate
Paleontologist Matt Friedman was surprised to discover a highly detailed 319-million-year-old fish brain fossil while testing micro-CT scans for a larger project.
Friedman of the University of Michigan says. “It’s got all these features and it’s like, ‘Is this really the brain I’m looking at?
“So we zoomed in on that part of the skull and did a second high-resolution scan, and it became clear that it was exactly what we needed. , we decided to aim higher.”
Usually, traces of such ancient creatures remain only from hard parts such as animal bones. Soft tissue deteriorates quickly, so it’s easier to store.
In this case, however, a dense mineral, presumably pyrite, was leached out and replaced the texture that would have been preserved longer in the hypoxic environment. This allowed us to capture details of the cranial nerves and soft tissue of the small fish Coccocephalus wildi.
Although the specimen has been in the hands of researchers since it was first described in 1925, this feature has remained hidden to avoid the risk of scientists using invasive research methods. It was.
“The fossils, which have been examined many times over the past century by multiple people, show a remarkable state of preservation,” Friedman explains.
“But new tools for looking inside fossils have revealed another layer of information.
This prehistoric estuary fish probably hunted insects, small crustaceans and cephalopods by chasing them with fins supported by bony sticks called rays.
Actinopterygii (subclass Actinopterygii) account for more than half of all living vertebrates, such as tuna and seahorses, and 96% of all fish.
This group diverged about 450 million years ago from the lobe-finned fish that eventually became our ancestors. C. wildi then evolved independently from a school of fish that still lives tens of millions of years ago.
“Analysis places this taxon outside the group that includes all extant ray fish,” write University of Michigan paleontologist Rodrigo Figueroa and colleagues in a paper.
“Thus, the details of the brain structure in Coccocephalus have implications for the interpretation of neuromorphology at early stages in the evolution of important vertebrate lineages.
Certain morphological details could still be discerned, although some brain features are lost during decay and preservation. They found that this prehistoric forebrain evolved more like our forebrain than any other living rayfin fish.
“The brain of Kokkokefalu is folded inwards, unlike all extant stingray fish,” Friedman says. “So this fossil predates the evolution of this feature that is characteristic of the ray brain, which was not very clear until the new data on Coccocephalus. It puts some kind of constraint on when the has evolved.”
Like us, the two cerebral hemispheres come to embrace a cavity that is a combination of the ‘V’ and its mirror image. In contrast, the forebrain of still-living ray fins consists of two lobes with only a thin notch between them.
Researchers are eager to examine other fish fossils in the museum’s collection to see if there are other soft-tissue imprints hidden inside.
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