A barb from a bird feather trapped in late Cretaceous amber (Image: Science/AAAS) Numerous filaments whose shape resembles that of fossilised dinosaur protofeathers, in late Cretaceous amber (Image: Science/AAAS) Late Cretaceous amber containing a cross section of a feather, with barbules that are coiled at their base. Such structures are found in modern-day diving birds (Image: Science/AAAS)


By the late Cretaceous, about 80 million years ago, birds had evolved feathers for flying or diving, but they lived alongside dinosaurs with primitive feathers like hair. Both kinds of feathers have been found together, preserved in amber.

The feathers offer a snapshot of late Cretaceous life, says Ryan McKellar of the University of Alberta in Edmonton, Canada. He identified 11 pieces of amber from the same Canadian deposit, dating from 79 to 78 million years ago. Two were donated by amateur fossil hunters, and the rest had sat unremarked in a museum for 15 years.

The amber, which is fossilised resin, contains fragments of feather between 2 and 8 millimetres long that were probably blown in as the resin dribbled down a tree trunk. Although small, they are exquisitely preserved.

The dinosaur feathers are primitive, thin filaments that look similar to mammalian hair but are much thinner and lack the scales that cover ordinary hair. Some appear to have been arranged evenly in a pelt, while others are in tufts. Their colour ranges from medium to dark brown. McKellar thinks the simple feathers helped keep dinosaurs warm, and endured until the animals died out.

By contrast, the preserved bird feathers resemble those of modern birds. McKellar says some are clearly flight feathers, in line with fossil evidence that flight had evolved long before 80 million years ago.

Others have a coiled design that would have absorbed water. Modern grebes have similar feathers to help them dive into water, suggesting that the Cretaceous feathers served the same purpose.

The co-existence of groups with primitive and advanced feathers had been suspected, but McKellar’s find is proof, says Mark Norell of the American Museum of Natural History in New York.

Journal reference: Science, DOI: 10.1126/science.1203344