Fossils of dinosaur with 4 wings found

Flight: A feathered creature that lived in northeast China 128 million years ago could fill in some blanks in the evolution of birds.

January 23, 2003|By Michael Stroh | Michael Stroh,SUN STAFF

Chinese fossil hunters have discovered a new creature that's as potentially significant as it is just plain strange: a four-winged dinosaur that swooped through the sky.

"It's weird, no question," said Thomas R. Holtz Jr., a vertebrate paleontologist at the University of Maryland, College Park.

While scientists don't yet know quite what to make of this bird-like beast, they speculate it could represent a previously unknown stage of avian evolution.

The fossil is also adding new wrinkles to one of the most fascinating evolutionary enigmas of all - how did birds first learn to fly?

In recent years, paleontologists have unearthed a growing menagerie of fossilized dinosaurs that appear to have once sported downy fur or feathers.

The discoveries have convinced many scientists that birds have a surprising pedigree: They're living relatives of the velociraptor and other toothy terrors from Jurassic Park, members of a carnivorous clan known as dromaeosaurs.

Because feathers appear to show up on dinosaurs long before any of them learned to fly, fossil evidence has also forced scientists to consider that plumage served other purposes, such as keeping dinosaurs warm.

But now Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and colleagues report finding six well-preserved fossils of an airborne dromaeosaur.

The creature, which they've dubbed Microraptor gui, was about the size of a tomcat and lived 128 million years ago.

The most startling thing about the fossils is the clearly visible outlines of feathers etched into the rock around the creature's front and rear limbs.

"The leg feathers are arranged in a pattern similar to wing feathers in modern birds," Xu reports today in the journal Nature.

In other words, the feathers on the rear legs apparently weren't for insulation or peacock-like frill, but for flight.

Exactly how the dinosaur used its four wings is something that will require computer simulation and careful study of the dinosaur's skeleton to puzzle out.

Because of the way the leg bones line up, Xu and his team don't think the dinosaur flapped its wings. Instead, the scientists speculate the 30-inch-long creature glided, much as a flying squirrel does today.

The fossils were all found in the remote hills of Liaoning, a province in the northeastern corner of China.

The landscape of low rolling hills and farmland was once a tropical forest dotted with lakes and ponds, which trapped and preserved plant and animal life in fine silt. The region has been the source of most of the significant feathered fossils discovered in recent years.

Scientists say the new four-winged dinosaur is likely to heat up the century-old debate over the origins of flight.

Over the years, scientists have proposed two theories to explain how prehistoric animals took to the sky.

The first is that fast-running feathered dinosaurs that lived on the ground eventually ran fast enough and flapped hard enough to muscle their way into the air.

Alternatively, in 1915 the naturalist William Beebe and others proposed that avian flight evolved in feathered, tree-dwelling creatures that first learned to glide. Beebe even proposed the existence of a four-winged creature dubbed tetrapteryx.

Although support for this imaginary creature failed to take off, the new Microraptor fossil "looks as if it could have glided straight out of the pages of Beebe's notebooks," says Richard Prum of the University of Kansas in an accompanying article in Nature.

The Chinese discovery, says Mark Norell at the American Museum of Natural History, shows that Beebe and other advocates of tree-dwelling flight might be right.

The four-winged dinosaur's long leg feathers probably would have prevented the animal from doing much sprinting.

But new research on modern-day birds is showing the story of flight might be even more complex than scientists imagined.

Ken Dial, a biologist at the University of Montana, has found that flightless ground-dwelling African birds called chukars use their wings to help scale mountains and other steep surfaces.

Dial reported last week in the journal Science that, by flapping wildly, chukars give their clawed feet more purchase, allowing them to perform daredevil-like stunts such as skittering up inclines as steep as 105 degrees.

That study, scientists say, seems to offer support for both a ground-based and a tree-based origin of flight.

Paleontologists say that only the discovery of more feathery fossils will answer lingering questions about the origin of flight and evolution of birds.

Instead of a missing link between dinosaur and bird, Microraptor gui, they say, might also turn out to be a dodo-like dead end.

"If birds did come from four-winged animals, it adds complication to the story," says Holtz.

"But it's an interesting one."

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