Six years ago a fossil of a 130 million-year-old creature with four wings and superbly preserved feathers was discovered in a stone quarry in China. Paleontologists had never seen anything like it. They aren't even sure how to reconstruct the fossils for an accurate depiction of the creature.
On Tuesday, February 26, 2008, NOVA, the highest rated science series on television and Public Broadcasting System's (PBS) most watched documentary series, airs "The Four-Winged Dinosaur". The hour-long program attempts to resolve the standoff debate among scientists regarding the origin of flight in birds by presenting two distinct reconstructions of the fossils and conducting an unorthodox experiment to determine whether a replica of the creature is capable of flight.
Four days later, on March 1, 2008, the exhibit "Feathered Dinosaurs and the Origins of Flight" opens at the Arizona Museum of Natural History in Mesa. The exhibit includes a collection 35 fossils that are national treasures on loan from the People's Republic of China along with life-sized reconstructions of how the animals may have looked.
"The NOVA program and our exhibit 'Feathered Dinosaurs' could not complement each other more," Arizona Museum of Natural History Curator of Paleontology Dr. Robert McCord said. "Both examine fossils from Liaoning Province, China and both explore the question: how do all these feathered dinosaurs change our understanding of the origin of flight and birds?"
The debate over how flight and birds evolved is not new. In his 1973 study of Archaeopteryx, paleontologist John Ostrom revived the theory, first made a century before, that modern day birds are the descendants of dinosaurs. As one of the earliest proponents of the theory during the twentieth century, one of the "winged dinosaurs", the Rahona ostromi, was named for him in 1998. Fossil remains indicate "Ostrom's menace from the skies" had feathers, a two-foot wingspan and a sickle-clawed second toe, when it roamed or flew the Earth between 65 and 70 million years ago.
Ostrem is not the only supporter of the theory. Even among those who believe dinosaurs are the ancient ancestors of birds, however, it is disputed as to how flight actually developed. Some argue that two legged, ground dwelling animals developed feathers and wings which allowed them to become airborne. Others hypothesize that flight developed among tree-dwelling creatures who, after generations of leaping limb-to-limb, developed gliding structures to soften landings and extend the length of the leap. These gliding structures eventually became wings.
Whether flight developed from the ground up or from the trees done does not alter the central theory that birds descended from dinosaurs.Not everyone agrees, of course.
"My idea," Larry Martin, Curator in Charge of the University of Kansas Natural History Museum, said in 1997, "is that birds separated off early from the [evolutionary] stalk that gave rise to crocodiles and dinosaurs --- well before there was anything you could call a dinosaur."He points to Longisquama insignis a small reptile that existed in central Asia some 220 million years ago and some 75 million years before the earliest birds. Martin co-authored a study with several other scientists theorizing Logisquama had feathers and glided among the trees above the earliest dinosaurs.
Research published online on January 28, 2008 in the journal BMC Biology, appears to support a pre-dinosaur ancestor for birds.
"Scientists typically use two sources of information to date biological events: the fossil record, which contains physical remains of ancient organisms, and molecular genetic data," explains University of Michigan graduate student Joseph Brown, who is first author on a new study suggesting the ancestors of modern birds arose more than 100 million years ago, not the 60 million years ago indicated by the fossil record. Brown and his fellow researchers from the University of Michigan, the University of Chicago, the Centre for Biodiversity Conservation Mexico and Central America and Boston University explain that fossils tend to underestimate the amount of time since lineages diverged and that the molecular clock used to reconstruct evolutionary history isn't quite as precise as was assumed.
"What my colleagues and I did was apply all these new methods to the problem of the origin of modern birds, with each method making different assumptions about how mutation rate changes across the tree," Brown explains. He says the researchers hoped to narrow the gap between the fossil and molecular data but the results in fact underscored the finding that the forebears of modern birds emerged more than 100 million years ago.
Mark Davis, producer of NOVA's "The Four-Winged Dinosaur" and its predecessor the "Case of the Flying Dinosaur" (NOVA, 1991), has been tracking the debate over the origins of flight and the search for bird ancestors for almost two decades. He doesn't expect to resolve it in a single hour.
"In 'The Four-Winged Dinosaur', we weren't trying to solve the puzzle but rather provide a glimpse into what makes it such a puzzle in the first place," he explains in the Producer's Story on PBS.org.
Viewers and visitors to the "Feathered Dinosaurs and the Origin of Flight" which opens March 1, 2008 at the Arizona Museum of Natural History can decide for themselves.
The Arizona Museum of Natural History is located at 53 N. McDonald St. in Mesa.
"Feathered Dinosaurs and the Origin of Flight" was organized by The Dinosaur Museum of Blanding, Utah in association with the Fossil Administration Office of Liaoning, China and the Liaoning Beipiao China Shihetun Museum of Paleontology.
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