The brain has been hiding inside a fossil fish skull and it's now revealing secrets of animal evolution. Illustration of a small gray fish with a dark stripe down its side with an extra bit showing what its little pink brain looked like.This artist's rendering shows what Coccocephalus wildi might have looked like back when it lived over 300 million years ago. - Márcio L. Castro A very long time ago, a fish died, was buried in sediments and eventually became fossilized. Today, 319 million years later, it's the star of a study that reveals "the oldest example of a...