First mammals show their true colors and it’s all dark

While some dinosaurs had beautiful, colorful feathers, mammals looked far less vibrant. Dark brown shades were the only colors their fur had for a long time. The researchers analyzed six different fossils, dating from 165 to 100 million years ago, and found that they all had a similar, uniform color. In these fossils, they examined melanosomes — microscopic cell structures that contain melanin and determine the color of skin, fur, and feathers. The researchers mainly found the type that contributes to brown and black shades and could even determine that dark brown tones were the most prominent.

It was already known that early mammals had many traits of nocturnal animals, such as large eyes and enhanced senses of smell, and the discovered fur color fits perfectly into that picture. Even today, we see that nocturnal animals often have a dark, uniform skin or coat. There is a strong suspicion that mammals only began developing interesting fur colors and patterns after the extinction of the dinosaurs, and then, things progressed rapidly. “Today, mammals come in a wide range of colors, but their coloration isn’t just for looks. It helps them survive by controlling body heat, blending into their surroundings, and attracting mates. By studying the appearance of early mammals, we can learn more about their lives and how today’s diversity began”, explains Liliana D’Alba.

New old mammal

The researchers have also discovered a new prehistoric mammal: Arboroharamiya fuscus, with 'fuscus' referring to its dark fur color. It was a small, squirrel-like mammal that resembled the modern flying squirrel. Its fossil had an exceptionally well-preserved coat, making it ideal for analysis.

More information

The scientific publication: 'Mesozoic mammaliaforms illuminate the origins of pelage coloration', published in Science.

Text: Jade Eversmann, Naturalis Biodiversity Center
Images: Chuang Zhao; Ruoshuang Li and others