Fossilised skin flakes have been discovered on a dinosaur that stalked the earth about 125 million years ago in the oldest known case of dandruff.
The flakes were among the feathers of the microrapter, a four-winged dinosaur that shows the evolutionary relationship between dinosaurs and birds.
The importance of the research, published in Nature, is it shows a key evolutionary difference between such dinosaurs and modern reptiles which shed their skin in one moult.
Study co-author Professor Mike Benton, from the University of Bristol, said: "This is the only ever reported fossil dandruff of any kind, so far as I am aware. So, the first from a dinosaur, the oldest and the first from any fossil."
The researchers were using an electronic microscope to study feathers from Chinese samples of the microraptor as well as feathered dinosaurs beipiaosaurus and sinornithosaurus, and the primitive bird confuciusornis.
They came across dead cells that form the skin's outer layer, corneocytes, which are very similar to those in modern birds and in human dandruff.
Crocodiles also shed their skin in fragments. Because they have a common ancestor with birds that also gave rise to the dinosaurs, the researchers suggested it was the original condition before some reptiles evolved the single-shedding process.
While the dandruff aspect is "a bit of fun", Prof Benton said, there is a "much deeper meaning" to the research.
Modern birds have fatty dandruff-like cells to help cooling by evaporation during the strenuous activity of flying.
However, the researchers said the cells in their birds were not fatty, suggesting that if they could fly at all, it was not for long periods.
