July 9, 2008

Scientists Find Hints Of Colors In Dinosaur Fossils

Scientists believe they have gained new insights into determining the colors of 100 million-year-old fossilized plumage from dinosaurs.

Researchers were able to determine the colors of ancient feathers found in Brazil displayed by "striking" bands of black and white, they reported in the journal Biology Letters.

Before now, fossil experts were left with only a guess at the various colors exhibited by ancient birds and some dinosaurs.

"It solves a conundrum," explained Professor Mike Benton of the University of Bristol, commenting on the work.

Researchers from Yale University found that the feathers had an obvious striped pattern, but were unable to determine whether it was from geological or biological origin.

"The banding looks so life-like that it can't be geological in origin - it has to be biological," said Professor Benton.

"But then how do you square that with the well-known fact that the majority of organic molecules decay in thousands of years?"

By comparing the ancient feathers to those of modern birds, researchers found that both displayed a distinctive granular texture, made from thousands of tiny, densely-packed flattened spheres. They had previously considered these to be fossilized bacteria.

"There are particular cells that cluster into the dark areas of modern birds called melanosomes," explained Professor Benton.

"Somehow [the melanosomes] are retained and replaced during the preservation process and hence you preserve a very life like representation of the color banding [in the fossils]."

Studies with modern birds showed that colors are linked to specific arrangements of melanosomes, which could be helpful in the reconstruction of ornate plumage.

The Yale team claimed it could identify brown, red, buff and even iridescent colors.

"It allows you in certain cases to combine this knowledge with other information to paint quite a remarkable picture of behavior," Professor Benton said.

For example, it could give researchers clues about courtship displays and mating behaviors.

"It might give you a very clear handle on an aspect of the ecology that people would have thought impossible to divine for an ancient fossil," said Professor Benton.

Another technique for revealing colors was displayed in 2006, when scientists found that some wooly mammoths had dark brown coats, while others had pale ginger or blond hair.

Scientists were able to gain this information by extracting genetic material from a 43,000-year-old woolly mammoth bone from Siberia. This technique is not as widely applicable to ancient dinosaur fossils because they tend to rarely be well-preserved specimens.


Image 1: Bird fossil from the Oligocene epoch, approximately 30 million years old.

Image 2: Striped fossil feather and recent woodpecker feather. Under the scanning electron microscope there are melanosomes in the dark but not the light areas (left arrows) of the fossil. For comparison, melanosomes from a broken black feather and a white feather are shown (right arrows). [Credit for image: J.Vinther/Yale]


On the Net:

Biology Letters

Yale University

University of Bristol