World's oldest preserved brain discovered in a 319 million-year-old fish fossil

Fish have not been famous for their cleverness and brains till now. A recent scan of the skull of a 319-million-year-old fossilized fish has shed light on the oldest example of a well-preserved vertebrate brain, revealing the early evolution of bony fish. The fossil of the skull, which was a part of the extinct Coccocephalus wildi was found in a coal mine in England almost a century ago, according to researchers of the study published in the journal Nature on February 1, according to CNN.

The fossil is the only remaining specimen of the fish species. Hence, scientists from the University of Michigan in the US and the University of Birmingham in the UK used the nondestructive imaging technique of computed tomography (CT) scanning to look inside its skull and study its internal bodily structure. After the scan, came the real surprise. The CT image showed an "unidentified blob," a University of Michigan press release said. The object was similar to vertebrate brains. It was bilaterally symmetrical, contained hollow spaces, and had multiple filaments (like cranial nerves). The brain folded inward, unlike in today's living ray-finned fishes.

Moreover, according to MyModernMet, vertebrate brains tend to decay quickly, so finding fossilized specimens is unusual. The dead critter may have been quickly enshrouded in sediment with low oxygen levels. Senior author of the paper Sam Giles of the University of Birmingham said in the university's statement, “This unexpected find of a three-dimensionally preserved vertebrate brain gives us a startling insight into the neural anatomy of ray-finned fish. It tells us a more complicated pattern of brain evolution than suggested by living species alone, allowing us to define better how and when present-day bony fishes evolved.”

“Comparisons to living fishes showed that the brain of Coccocephalus is most similar to the brains of sturgeons and paddlefish, which are often called ‘primitive’ fishes because they diverged from all other living ray-finned fishes more than 300 million years ago,” he noted. The modern world's 30,000 ray-finned fish species comprise half of this planet's vertebrate species.

"This is such an exciting and unanticipated find," co-author Sam Giles, a vertebrate paleontologist and senior research fellow at the University of Birmingham told CNN, adding that they had "no idea" there was a brain inside when they started studying the skull. "It was so unexpected that it took us a while to be certain that it actually was a brain. Aside from being just a preservational curiosity, the anatomy of the brain in this fossil has big implications for our understanding of brain evolution in fishes," she added.

Giles said, "The next steps are to figure out exactly how such delicate features as the brain can be preserved for hundreds of millions of years, and look for more fossils that also preserve the brain."

After this research, we might begin to know fish for their brains!