By Tara Haelle

By Michael DiGiogio

“I don’t think anyone’s ever dreamed that we’d be able to put color on dinosaurs,” Clarke said. “We only discovered the feathers 15 years ago, and we had skin impressions of skin texturing but no evidence for color. I don’t think we predicted that this kind of research would be possible.”

What made the research possible was a 2008 discovery by Yale graduate student Jakob Vinther, one of the “Science” paper’s co-authors, regarding the similarities between  certain skin pigment molecules across ancient and present-day animals. Pigment is determined by a chemical called melanin, contained within tiny organelles in cells that are called melanosomes. Vinther was studying the fossil preservation of mollusks when he compared molecules he was seeing in the fossilized ink sacs of ancient squid to what he saw in extant squid specimens today. The molecules in the ancient squid ink shared the same shape, which determined the color produced, as the melanosomes of the present-day squid ink. Round melanosomes produce reddish and brownish colors, and rod-shaped melanosomes produce blacks and grays. Or, as Vinther describes it, “the meatballs are red, and the sausages are black.” Slight variations in the densities and distribution of the melanosomes determine the specifics about the colors.

“I realized if melanin is everywhere else, then we can look at a feathered dinosaur, and we can put color on it,” Vinther said. “It actually worked. It’s pretty amazing.”

The technique requires a feathered dinosaur specimens’ fossilized feathers to retain the shapes of the melanosomes. Theoretically, Vinther said, this same technique could be used to determine the color of a non-feathered dinosaur’s skin if the researchers had dinosaur fossils with good enough skin impressions. Not too many fossils with well-preserved skin impressions exist though, he said.

Once Vinther discovered this method of skin determination based on melanosome shapes, he teamed up with Clarke and lead paleontologist Li Quanguo of the Beijing Museum of Natural History. The best specimens in the world for studying the feathers were in China, where an area of lakes containing ash from surrounding volcanoes has preserved the soft tissues of ancient animals better than in other parts of the world. Vinther’s discovery led another team, led by paleontologists Fucheng Zhang of China’s Institute for Vertebrate Paleontology and Mike Benton of the University of Bristol in England, to begin looking at possible coloration in dinosaur specimens using the same method. That team, which identified colors of only isolated parts of different species of dinosaurs, published their findings in the journal “Nature” one week before Clarke’s team’s article appeared in “Science,” which is the first article to publish the entire color scheme of a single specimen.

Photo by Tara Haelle

Aside from providing a more complete and colorful picture of certain dinosaurs, this discovery of the bright colors and patterns in dinosaur plumage raises significant questions about the purpose of dinosaurs’ feathers since the feathers developed before dinosaurs were able to fly. Although Clarke said they are confident that several of the smaller feathered dinosaurs from China did fly, there are many more who could not have gotten airborne because of their large body masses.

“What the new findings show is that the first time we see these anatomically modern feathers in the fossil record, they are patterned,” Clarke said. “We don’t have evidence that they were used in aerial locomotion, so it means they could have been used for signaling or communication or sexual selection or camouflage — all these other functions feathers have in birds related to plumage coloration.”

Clarke said scientists had noticed for years the bony similarities between dinosaurs and birds and hypothesized that birds descended from one lineage of dinosaurs. In 1996, researchers found the fossils of protofeathers, or early feathers, in the fossils of one part of the dinosaur family tree whose species already looked closely related to birds. Further discoveries of feathers in fossil specimens supported the theory that dinosaurs evolved into today’s birds. Clarke said she reminds students in her class that some dinosaurs never became extinct. The most common ancestor survived, giving rise to the more than 9,000 “feathered dinosaurs” around today — every bird across the world from the albatross to the zebra finch.

Now scientists know not only that dinosaur feathers share the same structure as bird feathers, but that they also share the same way of patterning their feathers.

“It’s more evidence that birds are most closely related to these groups of dinosaurs,” Clarke said. The evidence begins to fill in some answers and brings up more questions about the evolution of feathers.

“We know feathers did not originate for flight,” Clarke said. “Their origin seems to be equally if not more linked to signaling and communication, but this opens up more subtle, more interesting questions: What could we say about ecology? What was the pattern of evolution of feathering? We’re only beginning to understand the evolution of feather shape and feather distribution.”

Although Clarke will continue to work on her research specialty, the origins of birds and of flight, and Vinther will continue looking at ancient mollusks, both plan to continue making discoveries about the colors of prehistoric fossils.

“We’re hoping to collaborate to take this further, maybe to some other dinosaurs,” Clarke said.

Clarke estimated 500 to 1,000 different non-avian-related dinosaur species have feathers on at least parts of their bodies — some of them popular culture’s most beloved species. Tyrannosaurus Rex, for example, has smaller relatives in China that have feathers, and Vinther said there are more primitive ancestors of T. Rex who had protofeathers. T. Rex himself, therefore, quite possibly had feathers on his arms or his tail, or even downy feathers on parts of his body, though scientists do not have fossils presently to confirm this. Clarke said a new feathered dinosaur discovered last year falls very early on the dinosaur family tree, and she said new evidence might suggest that all dinosaurs have the filaments for early feathers.

If colorful feathers are not enough to challenge people’s conceptions of ferocious Jurassic carnivores, Vinther wonders what sounds the dinosaurs might have really made.

“T. Rex would be like a giant turkey,” he said. “What would the roar be like?” Or, quite possibly, what would the squawk sound like?