9 Jun 2011

Iridescent Feathers

Dinosaurs may soon show true colors

A team of paleontologists and ornithologists has discovered evidence of vivid iridescent colors in fossil feathers more than 40 million years old.

The simplest iridescent feather colors are produced by light scattering off the feather's surface and a smooth surface of melanin pigment granules within the feather protein.

Examining feather fossils from the Messel Shale in Germany with an electron microscope, researchers have documented the presence of melanosomes and studied their structure.

"Although fossil feathers have been known for many years, determining their original color has not been done," said H. Richard Lane, a paleontologist and program director in NSF's Division of Earth Sciences.
"Discovery of a color-producing nanostructure in a fossil feather opens up the possibility that we someday be able to determine such colors in fossil birds, as well as in feathered dinosaurs."

For more than 25 years, paleontologists have found microscopic tubular structures on fossilized feathers and hair. These were long interpreted as bacteria that had digested the feathers at the time they were fossilized.

The team had previously discovered that these structures were in fact not bacteria but melanosomes, which has allowed them to determine the original color patterns (melanosomes have distinctive shapes depending on the type of melanin they contain).

"The feathers produced a black background with a metallic greenish, bluish or coppery color at certain angles - much like the colors we see in starlings and grackles today," said Richard Prum, a scientist at Yale and one of the paper's authors.

Following up on the new finding, he and colleagues are racing to discover what additional coloration features may be found in fossil feathers.

"The discovery of ultra-structural detail in feather fossils opens up remarkable possibilities for the investigation of other features in soft-bodied fossils, like fur and even internal organs," said scientist Derek Briggs of Yale, a co-author of the paper.

"The 'Holy Grail' is reconstructing the colors of feathered dinosaurs," said Yale graduate student and paper lead author Jakob Vinther. "We are working hard to determine if this will be possible."

A 40-million-year-old fossil feather
From Germany's Messel Shale

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