The oldest brain ever found was officially unveiled this week, in the journal PNAS.

Researchers at the European Synchrotron Radiation Facility were using X-rays to image the inside of an ancient fish skull fossil when they discovered what they call “a strikingly brain-shaped structure” (press release, research paper – link live soon). They suggest the 300 million year old brain of the iniopterygian fish was mineralised due to microbes.

[This story may seem very familiar to those who were paying close attention to the recent AAAS conference.]

“Soft tissue has fossilized in the past, but it is usually muscle and organs like kidneys because of phosphate bacteria from the gut that permeates into tissue and preserves its features,” says paper author John Maisey, of the American Museum of Natural History in New York City (LiveScience). “Fossilized brains are unusual, and this is by far the oldest known example.”

The paper itself notes the discovery of a brain may seem merely an interesting curiosity: “a chondrichthyan, be it Carboniferous in age, must have possessed a brain,” the authors write. However Maisey believes that now it has been shown that brains can be preserved in such ancient fossils people can start looking for other examples (AP).

This could even lead to insights into brain evolution.

“It’s quite possible that brain fossils are actually more common, and we simply haven’t been able to find them,” says Maisey (Scientific American).

There’s even a nice 3D video model of the skull and brain:

Carl Zimmer on the Loom blog says:

You may be struck by how small the brain (yellow) is compared to the braincase (red). If the scientists are right, it’s a cautionary tale for those who would estimate the size and shape of ancient fish brains from their braincases. But perhaps, in the future, researchers will find more actual brains, and will be able to chart the evolution of these delicate organs in greater detail.

Image: PNAS