U. of Michigan researchers find 319 million-year-old brain in fossilized fish

Researchers at the University of Michigan (U-M) reportedly have found the oldest well-preserved vertebrate brain to date, which was discovered in a fossilized fish skull from a specimen in England more than a century ago.

The brain belonged to a now-extinct bluegill-sized fish that lived in an estuary 319 million years ago, according to a press release from the university.

“Not only does this superficially unimpressive and small fossil show us the oldest example of a fossilized vertebrate brain, but it also shows that much of what we thought about brain evolution from living species alone will need reworking,” Rodrigo Figueroa, the study's lead author and doctoral student at the university, said in the release.

Figueroa worked on the study as part of his dissertation under U-M paleontologist Matt Friedman. Sam Giles, with the London Natural History Museum and the University of Birmingham, also contributed to it. These scientists believe the fish probably ate small crustaceans, aquatic insects, and cephalopods. The discovery is said to offer a window into the neural anatomy of early evolution of the major group of fishes alive today. It also sheds some light into the preservation of soft parts in fossils of backboned animals. 

According to the release, the researchers used computed tomography (CT) scanning to look into the skulls of the early ray-finned fish. The goal was to gather internal anatomical details that provide information about evolutionary relationships. 

The skull fossil from the UK is the only known specimen of its species, so they could only use nondestructive techniques to examine it. Friedman wasn't looking for a brain when using the micro-CT scanner, but the mystery object had several features found in vertebrate brains. 

There is evidence of brains and other parts of the nervous system recorded in flattened specimens more than 500 million years old. One example was reported about 14 years ago when researchers found the preserved brain of a 300-million-year-old shark relative. 

However, sharks and other cartilaginous fishes hold few species compared to the approximately 30,000 ray-finned fish species.