Tuesday, September 1, 2009

First Trace of Color Found in Fossil Bird Feathers

Published: August 31, 2009

Birds, more than any other group of animals, are a celebration of color. They have evolved to every extreme of the spectrum, from the hot pink of flamingos to the shimmering blue of a peacock’s neck. Yet, for decades, paleontologists who study extinct birds have had to use their imaginations to see the colors in the fossils. Several feather fossils have been unearthed over the years, but they have always been assumed to be colorless vestiges.

Now a team of scientists has discovered color-producing molecules that have survived for 47 million years in the fossil of a feather. By analyzing those molecules, the researchers have shown that they would have given a bird the kind of dark, iridescent sheen found on starlings and other living birds.

This new method may allow scientists not only to reconstruct ancient birds more accurately. Birds evolved from ground-running feathered dinosaurs, and now it may be possible to determine some of the colors on them as well.

“I really do think we are moving from dinosaurs in black and white to dinosaurs in Technicolor,” said Julia Clarke, a University of Texas paleontologist who was a co-author of the new paper, published in the journal Biology Letters.

The new research got its start with squid. Jakob Vinther, a graduate student at Yale, was examining a fossil of a squid when he discovered that its ink sac was packed with microscopic spheres. They were identical to the pigment-loaded structures that give color to ink in living squid, known as melanosomes.

Knowing that birds make melanosomes in their feathers, Mr. Vinther decided to look for them in bird fossils. He knew that unlike the spherical melanosomes in squid, birds make sausage-shaped ones. “When I zoomed in on the fossils, it was nothing but these little sausages,” Mr. Vinther said.

But Mr. Vinther had to rule out the possibility that the sausages were bacteria that fed on the feathers after the birds died and then fossilized. He and his colleagues did that by examining an unusual fossil feather from Brazil with a pattern of dark and white stripes. Last year they reported that they found the sausage-shaped structures only in the dark stripes and none in the white ones. It is unlikely that the bacteria would grow in such an arbitrary pattern.


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