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Interviewees: Richard Prum & Jakob Vinther, Yale University
by Caroline Parnass
Yale University graduate student Jakob Vinther was studying a fossil squid from the late Jurassic period, about 150 million years ago. Looking at the darkly colored, organic material where the squid’s ink sac was, he wondered how, on occasion, these ink sacs are preserved in the fossils. So Vinther took a small sample from the specimen and viewed it under a scanning electron microscope. He was surprised to find that the ink granules in the sample were preserved with their original shapes.
“And this ink is composed of a pigment called melanin,” says Vinther. “I thought it was quite spectacular that you could actually recognize melanin in a fossil that is 150 million years old.”
Melanin is a natural pigment that gives the color to human hair and skin, as well as many birds’ feathers. Paleontologists have assumed for years that the small, rod-shaped objects they find on many fossil bird feathers under the microscope are bacteria that had eaten away the bird feathers and were fossilized along with the feather in a matted, organized fashion. Vinther points out that melanin granules in bird feathers are organized in a very specific manner that is easily recognizable.
When he looked at a fossil feather under the electron microscope, he says, “They were organized in the way that they are in a feather, so they are aligned according to the rays of the feather.” After observing these so-called “bacteria,” Vinther hypothesized that these objects were mot bacteria at all, but rather preserved melanin granules like he had seen in the fossil squid.
When Vinther showed his images to Richard Prum, a professor of ecology and evolutionary biology at Yale, Prum recalls, “I immediately was on Jakob’s side. I immediately thought that these things are melanin granules.”
The research team substantiated their claim by looking at a very rare type of fossil bird feather: one with black and white bands of color running horizontally. They found that while these melanin granules were found on the black portions of the feather, they could not be seen on the white portions.
The End of Artistic License?
This research now allows scientists to say things about the external appearance of fossilized species that would have never been possible to say prior to it.
“For centuries, people have been doing paintings or drawings, renderings, of fossil organisms, trying to understand what they may have looked like. Most of those have been entirely fantasy,” says Prum, adding, “This has been some of the first bit of science on something that is so vivid to us when we look at living animals today: What colors are they?”
This discovery could now allow us to predict the coloration of other fossilized remains.
“You quite often find fossil fish and fossil dinosaurs and birds where you have the eye preserved, and we have melanin inside the eye as well,” says Vinther. “You also find insects with color bands preserved. So I immediately thought, actually melanin might be much more wide-spread in the fossil record than hitherto accepted.”
Perhaps the most surprising and most exciting application of this research is that it may allow us to predict the colors of many dinosaurs.
“These include many of our most well loved dinosaurs,” says Prum. “Like velociraptor, the dinosaur that chased the kids around the kitchen in Jurassic Park, was actually fully plumaged.”
While these dinosaur feathers were not used for flight until the appearance of the transitional species Archaeopteryx, the first known bird, they were probably useful for warmth. Prum says we could even learn more about the color of one of the most famous dinosaurs of all, Tyrannosaurus rex.
Detail from The Age of Reptiles © 1966, 1975, 1985, 1989 Yale Peabody Museum. All rights reserved.
“In the classic mural The Age of Reptiles in the Yale Peabody museum, they depicted T-rex, which is one of the iconic, huge, bipedal, meat-eating dinosaurs,” he says. “Recent fossil discoveries have shown that the closest relative of these huge tyrannosaurids actually had tiny skin appendages or fossil feathers—’dino-fuzz.’ Our recent discovery of melanin granules in fossil feathers may allow us to reconstruct what some of these dinosaurs really looked like, and that’s going to depend on having more and exciting fossil specimens.”
The team has thus far only been able to recognize black, white and red/brown melanin granules. But more research is being done to look at the biochemical composition of the preserved melanin granules and see whether or not there is information that can help them distinguish between a greater variety of colors.
So could this mean that fearsome creatures like T-rex might have been bright and multi-colored rather than the dour grey-green that artists have typically imagined?
“Even now many of the fossil feathers of dinosaurs from the Liaoning of China have very well preserved feathers that indicate that they may have had … feather patterns like black and white spots or brightly pigmented patterns within the plumage,” says Prum.
Before you know it, pictures in textbooks may need to be redone with T-rex looking like a big macaw.
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