It was a fast-flying, feathered predator, with teeth and claws like razors and a tail like a raptor from "Jurassic Park." Many scientists call it the missing link between dinosaurs and birds, the best evidence yet that today's bobolink was yesterday's primeval carnivore.

"The teeth and the jaw are an obvious giveaway. It's a dinosaur," said museum curator Stephen Czerkas. "But the arms are extraordinarily long--longer than the legs--like a bird. It's a tremendously important animal. We've never seen anything like it."

The source of Czerkas's enthusiasm is a fossil he spotted at a gem and mineral show and bought for his Dinosaur Museum in Blanding, Utah. He immediately recognized what he had: another spectacular find from an ancient lake bed in China's Liaoning Province, emerging as one of the most important sources of Cretaceous remains in the world.

The new foot-tall creature, dubbed Archaeoraptor liaoningensis, is sharing center stage with two other new Liaoning dinosaur-birds in an exhibition that opened yesterday at the National Geographic Society's Explorers Hall.

For Czerkas and many paleontologists, the discoveries are the most convincing, and, perhaps, the last, evidence necessary to convince holdouts that the carnivorous dinosaurs known as theropods are the ancestors of modern birds.

"For me, the debate's been over for 10 years," said Philip Currie of the Royal Tyrrell Museum in Alberta, Canada, who helped identify the new fossils. "With these newcomers, we don't have just one type of dinosaur. It's kind of overwhelming."

The dinosaur-bird link has important implications for paleontology. If Archaeoraptor and its ancient cousins had feathers, as the new fossils powerfully suggest, then they were likely to have been warm-blooded, not the cold-blooded reptiles of the textbooks.

And while the other two new Liaoning dinosaurs--recovered by Chinese paleontologists from conventional excavations--did not have arms powerful enough to fly, they must still have needed their feathers for warmth or ornamentation.

The first of these, Sinornithosaurus millenii, "Chinese bird-reptile of the millennium," was an eagle-size animal with barracuda-like teeth and very long claws. Beipiaosaurus inexpectus, "surprising lizard from Beipiao," was seven feet tall--the largest feathered dinosaur discovered.

And logically, Currie continued, the dinosaur-bird theory should also embrace the larger theropods, such as the Velociraptor of "Jurassic Park" fame, and even Tyrannosaurus rex, the emperor of prehistoric meat-eaters.

But "there's no evidence of feathers on Tyrannosaurus rex," Currie said, and a warm-blooded, adult Tyrannosaurus would probably generate enough body heat to offset the need for extra insulation.

Still, National Geographic magazine is a believer. The November issue depicts a Tyrannosaurus parent roaring at the edge of its nest next to a hatchling covered with fuzz.

This proselytizing may eventually prove to be the theory's undoing, said University of Kansas paleoornithologist Larry Martin, who believes flying dinosaurs and birds developed along parallel tracks, rather than evolving one from the other.

"The National Geographic is already committed, but it will turn out to be an embarrassment," Martin said. "When people start to think of Tyrannosaurus rex with feathers, they won't accept it."

Also, Martin said that while Archaeoraptor and similar fossils have skeletal characteristics that bear a surface similarity to those of birds, these features differ in key respects from the clear evolutionary line that begins with Archaeopteryx, the 145 million-year-old German fossil generally regarded as the first true bird.

Finally, he noted, by the time the Liaoning stratum was laid down about 120 million years ago, "you're at the point where birds were already abundant and diversifying and changing."

But Currie said there is no reason why "relic species" cannot exist side-by-side with their descendants, and, indeed, Liaoning is an unusually rich site where an entire ecosystem--including dinosaurs, reptiles, fish, birds, small mammals and plants--appears to have been virtually frozen in time.

Scientists theorize that this unique formation was caused by an exploding volcano that sent a ball of poison gas, known today as a nuee ardente, rolling into the lake bed where it quickly asphyxiated every living thing.

This was followed immediately by a rain of fine volcanic ash, which killed the bacteria in the water and mixed with the suspended lake mud to create a gentle bath of primordial goo.

Today the goo has gelled around the dead creatures like a plaster cast, which, when carefully split apart, preserves the outlines of what apparently were once hair and feathers.

"We can finally say that some dinosaurs did survive," Czerkas said. "We call them birds."