Dinosaur 'missing link' unearthed in Utah

WASHINGTON, (Reuters) - Birdlike dinosaurs newly unearthed in Utah may be a missing link between primitive meat-eating creatures and more evolved vegetarians, U.S. researchers reported on Wednesday.

The 125-million-year-old fossils show features of two-legged carnivorous dinosaurs called maniraptorans, from which birds are believed to have evolved, they said.

The fossils also have leaf-shaped teeth, stubby legs and the expansive bellies of plant-eaters, the researchers reported in this week's issue of the journal Nature. The new species is named Falcarius utahensis, meaning "sickle-maker from Utah."

MISSING LINK

"Falcarius is literally a missing link," Scott Sampson, chief curator at the Utah Museum of Natural History, told a news conference.

"Falcarius is kind of half-raptor and half herbivore. This transition is triggered by a shift in diet." It appeared at around the time that tasty, nutritious, flowering plants appeared on Earth, he said.

"We know that the first dinosaur was a small-bodied, lightly built, fleet-footed predator," Sampson added. All other dinosaurs evolved from it.

"However, as with many radiations of major groups of animals, it happened so quickly that we really don't have much in the way of fossil documentation."

Falcarius provides part of the picture, he said.

The adult Falcarius would have walked on two legs and was about 13 feet (4 meters) long and 4.5 feet (1.4 meters) tall. It had strong forearms, sharp, curved, 4-inch (10 centimeter) claws and a long neck.

FEATHERED FIEND?

It probably had feathers and is the earliest North American example of a therizinosaur, a group that includes feathered dinosaurs found in southeast China and maniraptorans, including the Velociraptor, perhaps best known from the novel and film "Jurassic Park."

"(It) is the most primitive known therizinosaur, demonstrating unequivocally that this large-bodied bizarre herbivorous group of dinosaurs came from Velociraptor-like ancestors," said Lindsay Zanno, a graduate student in geology and geophysics who worked on the study.

She describes it as "the ultimate in bizarre ... a cross between an ostrich, a gorilla and Edward Scissorhands" - a film character that had scissors instead of hands.

"Falcarius shows the beginning of features we associate with plant-eating dinosaurs, including a reduction in size of meat-cutting teeth to leaf-shredding teeth, the expansion of the gut to a size needed to ferment plants, and the early stages of changing the legs so they could carry a bulky body instead of running fast after prey," said James Kirkland, Utah state paleontologist at the Utah Geological Survey.

ANCIENT GRAVEL

The fossils were excavated from ancient gravel at the Crystal Geyser Quarry, which produces cold water and carbon dioxide gas.

"A bunch of these animals were killed more than once," Kirkland said, adding that "hundreds, perhaps even thousands" of individual fossils were found.

Kirkland believes the animals perhaps lived in flocks or herds, were attracted to plants around the spring and occasionally poisoned en masse by gas or contaminated water.

"Mass mortalities are known in a number of dinosaur groups - both meat-eating and plant-eating dinosaurs," he said.

In the present-day area periodic outbreaks of botulism poisoning have been documented, he said. "Periodically, thousand of birds (are) killed overnight," Kirkland said.

"These things do happen. They happen today."