A tree dweller who lived 48 million years ago probably had a blue plumage, researchers say. Scientists studying a fossil of Eocoracias brachyptera have identified for the first time the remnants of color in a fossil.
Researchers studied 72 spring samples of modern birds in many different colors and 12 samples of organic material were carefully taken from the fossilized plumage of E. Brachyptera . The team then analyzed the shape and size of a type of pigmented cell structure called the melanosome in the feathers. Melanosome forms have been associated with certain colors in feathers and fur to paint a picture of ancient animals. For example, sausage-shaped melanosomes are believed to contain black pigment, and rounder flesh-bell-shaped casings produce a red-brown pigment ( SN: 6/22/1
9, p. 14 ).
Blue is one of the more difficult colors to achieve. Blue, green, and iridescent feathers are referred to as structural hues, like those of a hummingbird, because the production of these colors requires a specific setup in the barbs of the spring. The setup includes a spongy, air entrapment filled layer of keratin, a layer of black pigmented melanosomes superimposed
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For a bird dyed blue," the top layer is structured to break blue-wavelength light, "says Frane Babarović, evolutionary biologist at the University of Sheffield, England." The underlying melanosomes absorb the rest of the light. "
Keratin is generally not well preserved in fossils, but melanosomes are common, so Babarović and his colleagues analyzed whether they could distinguish the shapes of melanosomes in blue color from other colors.
Melanosomes The blue-stained modern birds as well as from E. brachyptera did indeed have a unique shape, the researchers report in the Journal of June 26 of the Royal Society Interface .These melanosomes were long (approx 1,400 nanometers) and relatively broad (about 300 nanometers), larger and rounder than melanosomes in black feathers and in contrast to those with reddish brown od iridescent colors.  The shape of the microstructure, however, resembled the pigmented melanosomes associated with the color gray. This can mean that blue and gray are evolutionarily connected. The overlap makes it difficult to know if an ancient bird was truly blue or, as is common in modern birds, gray. Once blue has developed in a particular family group, the color keeps appearing with other family members. Many of E. brachyptera 's modern relatives, such as kingfishers and kookaburras, have blue feathers, which makes it much more likely that the old bird did so too.
In bird feathers, melanosomes are involved in the production of. involved Different colors are available in different shapes and sizes. Black, brown and gray colors are produced solely by pigments in the melanosomes. Structural colors, whether iridescent or blue or green, are generated in two steps: light is refracted by a keratin layer filled with air bubbles in the barbs of a spring, and an underlying melanosome layer absorbs the remainder of the scattered light wavelengths. But there is an overlapping area: The melanosomes for noniridescent structural colors are similar in size and shape of :. gray pigment melanosomes
" It's something that has not been researched that much, "says Klara Norden, an evolutionary biologist It's really exciting to have this study showing the shape of these melanosomes. "
Matthew Shawkey, evolutionary biologist at Ghent University in Belgium, notes that it's difficult is to distinguish between blue and gray Without knowledge of the pedigree of a fossil, the finding can only be used to a limited extent to identify the colors of other ancient birds.
Nevertheless, Shawkey says, "It is a neat and unexpected study." Blue leather structures also contain black pigment, "I did not expect them to look any different" than the melanosomes that are involved in the production of black paint, he says. "That was surprising."