"[Anchiornis] exhibits some wrist features indicative of high mobility, presaging the wing-folding mechanisms seen in more derived birds," he said.
"The wrist is a big part of the formation of wings, and pivotal to flight," Xu added. "During flight, steering and flapping greatly depend on the wrist."
Despite this protobird's relatively advanced feathers and wrist, it is unclear if Anchiornis could actually engage in powered flight.
"Behavior and biomechanics are very difficult to determine solely from the fossil record, and perhaps flight is impossible to determine," said Mark Norell, chairman and curator of the division of paleontology at the American Museum of Natural History in New York.
"Feathers have lots of functions, and probably evolved as thermoregulators," said Norell, who closely examined the fossil during a trip to Beijing.
"Dinosaurs might have used feathers for sexual display or to make themselves appear bigger, or as camouflage to avoid predators," he said.
Patterns of spots and bars evident on one species of feathered dinosaur from China might have functioned as a camouflage defense, Norell added.
(Related: "First Dinosaur Feathers for Show, Not Flight?" [October 22, 2008].)
Xu said that the region in northeastern China where most of the world's feathered dinosaurs, including Anchiornis, have been discovered is a virtual paradise for dinosaur hunting.
"This area has three circles of volcanic activity," with eruptions that intermittently covered and preserved entire biospheres starting from the early Jurassic.
"Volcanos periodically killed the animals and plants and preserved them perfectly in volcanic ash," he said.
"Sometimes the volcanic ash even preserves soft tissues, leaving behind an exceptional 3-D fossil."
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