What's a brain like? Kind of mushy, isn't it, like custard or pudding? Can you imagine how quickly it must break down in the decaying process of dead organisms? Brains just don't make it into the remains of most fossils. This YouTube video represents the exception.

Here is a YouTube video of a 300 million-year-old ratfish skull. Don't know about ratfish? They do exist today and are similar to sharks and rays. Note that the brain (yellow) is much smaller than the braincase (red). A fossilized brain...highly unusual.

Because of the fragile, highly organic nature of brain tissue, it is often one of the first organs to disintegrate in deceased animals. Scientists have often speculated about brain size in fossils by estimating the size based on the size of the braincase. But this video reveals how much smaller the actual brain can be in Sibyrhynchus denisoni, the genus-species name of this ratfish relative.

As the video progresses, the external skull sluffs away, followed by the braincase (red) and ending with the brain itself (yellow).

The 3-D animated image is thanks to the work of Alan Pradel of the Museum National d’Histoire Naturelle in Paris and his colleagues.