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A fuller picture of dinosaur feathers

Two recent studies describe the plumes on the Sinosauropteryx and the Anchiornis huxleyi, and some researchers suggest the colorful displays were used not for flying or insulation, but for visual appeal.

February 13, 2010|By Amina Khan
(Michael DiGiorgio / Yale )

Do studies of a feather flock together?

It certainly seemed that way when two reports on the coloration of early dinosaur feathers were released a week apart. Courtesy of the discoveries, creators of the next "Jurassic Park" knockoff can now render the fuzzy or feathered reptiles in vivid -- and accurate -- Technicolor.

One study, published Jan. 27 in the journal Nature, revealed the presence of "ginger" coloring in ancient feathers of several bird and dinosaur fossils. Notably, the scientists from Britain, Ireland and China described the orange crest and orange-ringed tail of the tiny 125-million-year-old Sinosauropteryx, a dinosaur that had primitive, bristly plumes not unlike those of the modern-day kiwi.

The other study, published Feb. 4 in the journal Science, colored in a complete picture of the four-winged, 155-million-year-old Anchiornis huxleyi. The U.S. and Chinese researchers determined that the dinosaur was covered in black and white plumage but sported a reddish, mohawk-like crest.

To determine the color of feathers, both teams looked for melanosomes, packets of the pigment melanin. The melanosomes' shapes revealed what colors the feathers would have been: In modern birds, more oblong-shaped melanosomes carry pigment that gives rise to black-gray tones. Spherical ones hold the melanin that makes brown-to-red hues.

In the case of Sinosauropteryx, finding melanosomes in the fuzzy material that covered its body confirmed that the fuzz was, in fact, primitive feathers. Because the structures lacked shafts and veins of modern bird quills, some scientists had argued that they were "shredded skin" made of collagen fibers.

Researchers are still tussling over whether feathers evolved first for flight, insulation or sexual display, and the new studies offer clues.

The bristly, primitive feathers of Sinosauropteryx could not have been used for flight, reasoned Michael Benton, a paleobiologist at the University of Bristol in England, a co-author of the Nature report. And because the dinosaur had feathers only on parts of its body, they could not have worked well for insulation, he added.

"That both of these early dinosaurs . . . have bright banding, all of it suggests something visual, doesn't it?" he said.

The candy-striped tail of Sinosauropteryx and the flashy mohawk of Anchiornis huxleyi suggest that feathers were first used to show off to potential mates or intimidate competing suitors, the two teams said.

After all, modern birds have complex mating patterns and use their plumage in displays, said Jakob Vinther, a Yale University graduate student and a co-author of the Science study. Others aren't so sure.

"There are other options, and I don't think we can rule them out so easily," said Luis Chiappe, director of the Dinosaur Institute at L.A.'s Natural History Museum, who was not involved in the research. Some feather patterns could have served as camouflage, he said.

And, he added, since reptiles can display color right on their skin without feathers, he thinks it is unlikely that dinosaurs would have evolved another structure for that purpose. Chiappe predicted that full-body analyses of a host of feathered dinosaurs will soon follow. "We're seeing dinosaurs in an entirely new way," he said.

amina.khan@latimes.com

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