Clues to feather’s technicolor past

YALE (US)—Signs of vivid iridescent colors have been found in feather fossils more than 40 million years old. The discovery could pave the way for determining color features of other ancient birds and even feathered dinosaurs.

Using an electron microscope, scientists from Yale University examined feather fossils from the Messel Shale in Germany and found a smooth layer of melanin structure called melanosomes. It is the first evidence of a preserved color-producing nanostructure in ancient feathers.

Iridescence is the quality of changing color depending on the angle of observation, such as the rainbow of colors seen in an oil slick. 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.

“These 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,” says  paper coauthor Richard Prum, chair of Yale’s ecology and evolutionary biology department.

For more than 25 years, paleontologists have found microscopic tubular structures on fossilized feathers and hair, and interpreted them as bacteria that had digested the feathers at the time they were fossilized. Further research showed that these structures were in fact not bacteria but melanosomes, which then allowed them to document the original color patterns.

Following up on the new finding, the researchers are hoping  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,” explains coauthor Derek Briggs, Yale’s Frederick William Beinecke Professor of Geology and Geophysics.

“Of course, the ‘Holy Grail’ in this program is reconstructing the colors of the feathered dinosaurs,” says Yale graduate student and lead author Jakob Vinther. “We are working hard to determine if this will be possible.”

Researchers from the University of Texas at Austin and Senckenberg Research Institute in Germany contributed to the paper which was published Aug. 26 online in Biology Letters. Funding was provided by the National Science Foundation, the National Geographic Society, and Yale University.

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