Published February 4, 2010
That may sound familiar, given last week's announcement of the first scientifically verified dinosaur color scheme.
But the previous research, published in Nature, had found pigments only on a few isolated parts of dinosaurs (see pictures)—and had used less rigorous methods for assigning colors to the fossilized, filament-like "protofeathers" found on some dinosaur specimens, say authors of the new report.
Both studies raise hopes that improved knowledge of dinosaur coloration could lead to insights into how some prehistoric animals behaved and why feathers evolved in the first place.
The subject of the new study—the 155-million-year-old Anchiornis huxleyi—turns out to have looked something like a woodpecker the size of a chicken, with black-and-white spangled wings and a rusty red crown (see animation above).
The color patterns on Anchiornis's limbs are "quite similar to the silver-spangled Hamburg chicken, a domestic breed of ornamental chicken," said ornithologist Richard Prum of Yale University. Prum is a co-author of the new study and has received funding from the Committee for Research and Exploration of the National Geographic Society (which owns National Geographic News).
Only a short time ago Anchiornis was completely unknown to science. The chicken-size dinosaur species' color patterns were decoded after the researchers had used a scanning electron microscope to study pigment samples taken from fossil feathers all over a specimen and then compared the samples to pigment from modern birds.
"Striking" Feather Finding
The new revelation is the second stage of what amounts to a photo finish in the race to be the first to report on scientifically established color in a fossil nonbird dinosaur (many paleontologists classify birds, even modern species, as dinosaurs).
They report that a complicated pattern of reddish brown, black, gray, and white feathers covered the fossilized dinosaur, leading to speculation that perhaps this coloration was used for attracting mates or some form of visual communication, as is often the case in living birds.
The new find's implications for the evolution of feathering and flight are "striking," said study co-author Julia Clarke, a vertebrate paleontologist at the University of Texas in Austin.
Anchiornis shows that, "when elongate feathers first appear [in the fossil record], they are already distinctively spotted and striped," Clarke said. "We now have patterns within individual feathers in dinosaurs long before we get some kind of aerial locomotion."
Yale's Prum added that "a more likely function"—other than flight—"for both the crown and limb feathers of Anchiornis is communication or signaling.”
"This could have been in lots of contexts, including sexual display, territoriality, et cetera," Prum said. "It could also have been like modern redstarts, which use their bright wing and tail patches to scare up insects, which [the birds] then seize in flight."
Diving Deep Into Dinosaur Pigment
The team behind the new study, in Science, determined the feather colors by analyzing the shape and density of melanosomes within fossil feathers. Melanosomes are nanoscale, pigment-bearing organelles within feathers.
The microscopic particles were first found preserved in a fossil—in this case, a prehistoric bird—by Vinther and his team in 2008. The particles had previously been interpreted in fossils as bacteria.
In modern birds, different types of melanosomes are known to produce different colors in feathers. Eumelanosomes are rodlike and are associated with the colors black and gray. Phaeomelanosomes are round and produce colors ranging from reddish brown to yellow. A lack of melanosomes makes white.
Coloring the Whole Plumage
The Nature team studied many different fossils but artistically recreated only one, used fossil-feather melanosomes to infer reddish-brown and white stripes on the tail of a small carnivorous dinosaur called Sinosauropteryx.
But while the earlier paper was the first to reveal coloration in dinosaurs, the new report goes further.
Derek Briggs, a co-author of the new study, said, "The other team's report is based on isolated samples from several different taxa, so they can't paint an entire animal."
Even so, the earlier study did include a picture of an entire Sinosauropteryx, but any coloration beyond the tail and the crest running along its head and back was artistic guesswork.
By contrast, Briggs said, "We have 29 samples from the same specimen, covering the whole plumage."
Finding Shades of Gray in Dinosaurs
The researchers behind the new study also say they were more meticulous in how they interpreted pigment samples.
Whereas the team behind the earlier study reported results from a few isolated fossil samples taken from several feathered dinosaurs and early birds , the Anchiornis team concentrated on one specimen. They took measurements of the melanosomes from 29 tiny samples collected from various places on the surface of the fossil and compared them to the size ranges and shape ranges—as well as the arrangements of—melanosomes in the feathers of living birds.
"This allowed us to interpret color to a more sophisticated degree—gray, for example, forms in different ways—and to express our results in terms of probability," Briggs said.
Also unlike the team behind the Nature study, the Anchiornis team directly related melanosome shape and size—not just type—to color, said Matthew Shawkey of the University of Akron, Ohio, a biologist on the project.
"This eliminated some shaky assumptions about how melanosome type relates to color," Shawkey added.
For example, Shawkey noted that the melanosomes found by the other team in the tail of Sinosauropteryx are all phaeomelanosomes—which he suggests can't necessarily be used to ascertain accurate color.
"Very few modern birds have 100 percent phaeomelanosomes or eumelanosomes in their feathers." So inferring color from phaeomelanosomes alone is tricky business, Shawkey suggests.
"What may appear at first glance to be black or brown may actually be gray"—a color created by a wide variety of melanosome shapes and densities.
Starting Gun: How the Hunt Began
The starting gun for the race to scientifically color dinosaurs was fired in 2008, with the Vinther team's discovery of melanosomes in fossil bird feathers.
Based on the find, Vinther recalled, "I thought we could color dinosaurs. I remember thinking, This is big, really big."
Vinther immediately helped assemble an international team which received a National Geographic grant to test for melanosomes and color in 50 million-year-old bird feathers from Germany and in much older feathered dinosaurs from China (prehistoric time line).
At the time, the other team, led by Fucheng Zhang and Mike Benton, was studying feathered dinosaur fossils in China to understand the circumstances of their exquisite preservation.
Once the Zhang-Benton team learned of the Vinther group's melanosome discovery, though, they began searching for the tiny organelles in their specimens—and striving to decode dinosaur color.
"I cannot guarantee we would have seen this if we had not seen the Vinther paper," Benton said.
When the Li Quanguo-Jakob Vinther team arrived in China, they expected to have access to many well-preserved feathered dinosaurs, but the researchers found that the Zhang-Benton team had already reserved many of the best fossils for its study, already in progress.
But within the Beijing Museum of Natural History collections, the Li-Vinther team found a dinosaur skeleton preserved in an ochre-colored slab of mudstone that looked like it might be well suited for melanosome study. Fossilized feathers burst from the dinosaur's bones in every direction—and showed faint evidence of dark and light markings.
It was only later that the Li-Vinther team established that their fossil was a specimen of Anchiornis—a species first identified in 2008 by a other scientists.
What's Next for Dinosaur Color?
"When Jakob [Vinther] contacted me to join a team that was actually going to reconstruct the colors of a dinosaur, I didn't think twice," said Shawkey, the University of Akron biologist.
"The reality of what we achieved didn't really sink in until I saw the color reconstruction," he added. "At that point I felt very emotional, like we had ... brought something back from the dead—or at least gone back in time and taken its picture."
For paleontologist Philip Currie, who wasn't part of the new research, the new study makes good on the promise of much earlier research. "Ever since we reported the first dark and light banding in dinosaur feathers in 1998, I figured there was a good chance that there might be traces that could tell us what some of the colors might have been," said Currie, of the University of Alberta in Canada.
"I am not sure that all artists will like the fact that we can now actually figure out the colors of some dinosaurs," Currie added, "because over the years we have taken away more and more of their artistic license as we've learned the intimate details of dinosaurian anatomy."
Paleoartist Gary Staab agrees. "In some ways the discovery of the true color of dinosaurs takes away a bit of the fun from building models for museums. Yet it does allow us to view these animals at a much higher 'resolution' than we have previously been capable of.
"No longer will coloration be a best guess, at least in this group of animals," Staab said.
(Related pictures: "What's Wrong With This Picture? An Audio Critique [of Dinosaur Art].")
The importance of identifying coloration of dinosaurs goes beyond artwork, however.
"The significance of these finely preserved feathered dinosaurs and early birds is that they pose questions we didn't even know to ask," said Clarke, the University of Texas paleontologist.
"In some ways the story is just opening up, and we can't predict where it is going."
More Dinosaur Color News
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