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Fossils, now available in color

A closer look at fossilized feathers suggests pigment may have been preserved

5:56pm, July 8, 2008
Magazine issue: Vol. 174 #3, August 2, 2008
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Researchers have found what appear to be remnants of pigment in fossilized feathers, opening the possibility of reconstructing the colors of many long-extinct animals.

Dark stripes in a 100-million-year-old fossilized feather — coming from an early bird or a dinosaur — contain particles that closely resemble, in size and arrangement, black melanin particles in modern bird feathers, paleobiologist Jakob Vinther of YaleUniversity and colleagues report in an upcoming Biology Letters. The team also found the particles in a bird fossil dating back to 50 million years ago.

Researchers had noticed the dark, carbon-rich microscopic granules in fossilized feathers already in the 1980s, but had assumed them to be remnants of bacteria that had decomposed the original organism.

But a direct comparison with modern feathers, using a scanning electron microscope, suggests otherwise, Vinther says. The particles have the size and shape of melanin particles. They are also arranged in similar patterns. “You wouldn’t expect bacteria to be aligned according to the orientation of the feathers,” he says.

Michael Benton, a paleontologist at the University of Bristol in England, says it’s “amazing” that the stripes seem to reflect the original patterns in the animal’s feathers. It will now be interesting to find out the exact chemical composition of the fossilized granules, he says. The fossils may not contain any actual melanin, Vinther says, since most organic matter breaks down before fossilizing. However, he says, “melanin is very resistant to degradation,” and his team is now attempting a chemical analysis of a few micrograms of the material to find out if some has survived intact.

Melanin is ubiquitous in the animal kingdom. Vinther says that researchers could now look for it in a wide range of fossils, including ichthyosaurs (giant marine reptiles), dinosaurs, insects, mollusk shells and mammals.

And while the shape of the granules is evidence of black pigment, yellow and red kinds of melanin also exist — such as in the freckles of fair-skinned humans. Cells tend to accumulate different types of melanin in sacs of different shapes, so paleontologists may be able to find evidence for actual colors, rather than black or shades of gray. And some animals create iridescent patterns by nanoscale structures of melanin, which might also be preserved in fossils.

Paleontologist Philip Manning of the University of Manchester in England comments that the presence of black melanin indeed provides a “very monochrome view” of the fossils, rather than a full-color picture. However, “preservation of a range of color signatures appears more than possible,” he says. “Once more in paleontology the preservational paradigm has been gently shifted in a positive direction.”

Viewing fossils in color could reveal how the animals dressed up for courtship, for example, while finding camouflage patterns could cast new light on the environments the animals roamed in, Vinther says.

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