Some 125 million years ago, a bizarre — and probably feathered — dinosaur roamed Utah, a creature considered a key "missing link" that may have marked a transition from meat-eating predators to vegetarians.

The discovery of the new species, Falcarius utahensis, was announced by scientists Wednesday. It is in the family of maniraptorans, a dinosaur group that included predators such as the Utahraptor and the Velociraptor — the vicious dinosaurs in "Jurassic Park." Falcarius had characteristics of both meat- and plant-eaters.

Two mass boneyards of the creatures were discovered near evidence for ancient springs south of Green River and close to the present-day Crystal Geyser in Grand County.

State paleontologist James Kirkland said Wednesday that bones from hundreds or thousands of dinosaurs are believed preserved at the quarry. About 99 percent are Falcarius, with specimens of all ages, from babies to adults. That indicates mass die-offs happened rather than bones accumulating over time, because it's hard to believe so few other types would be in the vicinity over the years, he said.

Falcarius is a former missing link, "which, of course, now is no longer missing," said Scott Sampson, chief curator at the Utah Museum of Natural History on the University of Utah campus.

A scientific paper describing the new animal was being published in today's edition of the scientific journal Nature. The authors are Kirkland; Lindsay E. Zanno, a U. doctoral student; Sampson; James M. Clark of George Washington University in Washington, D.C.; and Donald D. DeBlieux of the Utah Geological Survey.

The dinosaur dates to the early Cretaceous era, a period about which little is known in this country because of the scarcity of remains. But the Cedar Mountain Formation that curves through much of east-central Utah preserves important dinosaur fossils from the period, such as the carnivorous Allosaurus (Utah's "state dinosaur"), the Utahraptor and the herbivorous Gastonia.

Kirkland said the newly discovered Falcarius utahensis ("sickle-maker from Utah," referring to its claws) first came to his attention when he realized fossils were being sold on the black market. After he tried and failed to find the site, a Moab man who had illegally removed the vertebrate fossils from the federal land "took me directly to the site," he said. He told the man that if he were asked he'd have to say where the bones came from.

The Bureau of Land Management asked Kirkland to make a deposition about the find, and Kirkland told what he knew. As a result, the Moab man pleaded guilty to theft of government property and was sentenced to five months in prison, 36 months of supervised release and a $15,000 fine.