An artist’s illustration of a Microraptor with its iridescent plumage (Image: Jason Brougham/University of Texas) The exquisitely well-preserved fossil of a Microraptor (Image: Mick Ellison) A close-up of the preservation of the Microraptor’s feathering (Image: Mick Ellison) A reconstruction of the Microraptor, with colouring inferred from the current study and plumage based on the new fossil and previous specimens (Image: Science/AAAS) Advertisement

The unusual four-winged dinosaur Microraptor may have been coated with dark, iridescent feathers, an analysis of a newly discovered fossil suggests. The exquisitely preserved specimen also reveals that the 130-million-year-old beast carried a pair of long thin tail feathers. Both features suggest that early feathers evolved as much for display as for insulation, before they were adapted for flight.

Matthew Shawkey at the University of Akron in Ohio and colleagues used a scanning electron microscope to work out the colour and sheen of the fossil’s feathers, using a technique developed by co-author Jakob Vinther, now at the University of Texas at Austin. Vinther recently used the approach to show that a feather from Archaeopteryx, a 150-million-year-old early bird, was black.

Microraptor feathers were also black, the new analysis reveals: they are full of tiny structures called melanosomes that contained light-absorbing pigment. The melanosomes’ shape and arrangement is similar to that seen in living birds with iridescent feathers, suggesting that Microraptor also had an iridescent sheen.

Shake a tail feather

The new fossil is the first to clearly preserve the tip of Microraptor‘s long thin tail. Two thin feathers emerged at the tip, but they would have had little aerodynamic effect and may even have impaired flight, says Shawkey.

It’s more likely that the tail feathers were used for display, says co-author Julia Clarke, also at the University of Texas. Other dinosaurs living in China at the same time had patterned tails that may have had a similar function.

It is possible that the feathers’ iridescence added to the display. However, iridescence may evolve for other reasons. Earlier this year, Shawkey reported that golden moles have iridescent fur despite being blind burrow-dwellers. He speculated that the feature may help the mammals shed water or slip through their burrows with lower friction.

Knowing the colours of fossil animals “gives insight into what evolution is doing”, says Alan Brush, an ornithologist at the University of Connecticut in Storrs who was not involved with the study. Microraptor belongs to the group of dinosaurs from which birds evolved. “This says birds have been using plumage patterns to tell each other apart since the dawn of their evolution,” says Brush.

Journal reference: Science, DOI: 10.1126/science.1213780