One-hundred thirty million years ago, a dinosaur approximately the size of a pigeon soared through the skies on shiny, blue-black feathers. Although it looked like a bird, Microraptor, whose fossils are from northeastern China, did not, in fact, fly. Paleontologists believe that Microraptor, as a member of the dromaeosaur group of dinosaurs (closer to Velociraptor than to modern birds), glided through the air rather than actively flying, even though it had four wings rather than two (that is, its “legs” were also “wings”).

Newly discovered, however, is the color of the feathers on those wings. Quanguo Li of the Beijing Museum of Natural History and Matthew D. Shawkey of the University of Akron in Ohio, along with several other colleagues, used scanning electron microscopy to compare the fossilized cells that hold pigments in Microraptor feathers, known as melanosomes, to similar cells in modern birds. They found that the dinosaur’s melanosomes are narrow and stacked in layers, like those of birds today that have iridescent feathers—think blackbirds or crows. Non-iridescent feathers have round or oval melanosomes. [The idea is similar to the difference between mother-of-pearl and chalk—both of which are made of calcium carbonate crystals, just arranged differently.] This suggests that Microraptor also had shiny, iridescent feathers. Li and Shawkey hypothesize that the standout feathers were an evolutionary adaptation to attract mates. Supporting this idea is the presence in Microraptor of a striking pair of long, narrow tail feathers, probably a device to call attention to individuals during courtship.

Melanosomes
Melanosomes of various birds, including those of Microraptor (F).

This is the earliest known evidence of iridescent color in feathers. It also provides strong evidence, notes coauthor Mark Norell of the American Museum of Natural History in New York, that Microraptor was diurnal (active during the day), rather than nocturnal (active at night)—dark glossy plumage is not a characteristic typical of modern nighttime birds.

Find out more at Discover Magazine online.

The original article can be read in the journal Science.

Published On: April 17, 2012

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