Fossils reveal what the fur of early mammals looked like
A study of the fossilised fur of six mammals from the Jurassic and Cretaceous periods has found they were all greyish-brown in colour, which would have helped them hide from dinosaurs
By Michael Le Page
13 March 2025
Illustration of Arboroharamiya fuscus, a newly discovered Jurassic mammal species with dark fur
Chuang Zhao, Ruoshuang Li
While many dinosaurs and pterosaurs flaunted flamboyant feathers, early mammals were a dull lot. A study of the fossilised fur of six mammals that lived during the Jurassic and Cretaceous periods has found they all had greyish-brown fur.
“They were dinosaur food,” says Matthew Shawkey at Ghent University in Belgium. “You didn’t want to be conspicuous.”
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Working out what animals that lived in the distant past looked like used to be thought impossible. But since the 1990s, thousands of fossils with feathers and fur have been discovered.
In some cases, traces of melanosomes – cell organelles that contain the pigment melanin – can be seen when these fossils are examined under a microscope.
Melanin comes in two variants – black-brown and yellow-red – and the shape of melanosomes varies according to their composition. So, knowing the shape of melanosomes in fur or feathers gives you a good idea of their colour.
