A lost branch of dinosaur family

When James Kirkland first walked the barren, mudstone hilltop in the Utah desert four years ago, he was stunned by how many fossils littered the ground.

His excitement was tinged with regret, however. Dr. Kirkland knew that his guide, Lawrence Walker, was sharing a secret that probably would lead to Mr. Walker's prosecution for taking dinosaur bones from the site. It was federal land. And Walker, a commercial collector, had no permit to dig there. But Walker also sensed he'd found something truly remarkable on this remote patch of sandstone buttes and mesas. He agreed to lead Kirkland - Utah's state paleontologist - to the site and risk the consequences.

"I was overwhelmed," Kirkland recalls. "I put my hand on his shoulder and told him: 'I'll have to give a deposition if I'm asked to, but I am very grateful you chose me' " to see the site.

Grateful indeed. A team of paleontologists led by Kirkland announced Wednesday the discovery of a new dinosaur caught in the evolutionary act of shifting from a meat eater to a vegetarian.

The 125-million-year-old creature is expected to shed light on this process not just for the dinosaur's group itself, but for dinosaurs generally, the researchers say.

Moreover, its appearance in North America may deal a blow to the idea that the group originated in Asia. And it may become one of the most thoroughly studied dinosaurs in history. The hilltop is a mass burial ground for the animals. The new find, dubbed Falcarius utahensis, may have hundreds of its brethren interred there in well-preserved condition.

In the world of paleontology, that's a big deal. The overwhelming majority of the roughly 900 dinosaur species known are represented by a partial skeleton or a few bone fragments, Kirkland explains. "We estimate that there are well over a million bones here, and 99 percent are from this animal," he says. "This animal will be a hallmark dinosaur one day."

In its heyday, Falcarius measured 13 feet from beak to tail. It stood 4-1/2 feet tall and boasted talons four inches long. To the uninitiated, it resembles its Velociraptor cousin in many ways. But on closer inspection, the creature is clearly demoting itself on the food chain, the researchers say. Its teeth are losing their meat-eating edge. Its pelvis is broadening to accommodate a digestive system large enough to handle a plant-based diet. Its neck is growing longer, its legs stubbier, and its head smaller. In all, Falcarius displays 20 features of plant-eating dinosaurs that it appears to have evolved independently from other herbivores, according to Lindsay Zanno of the University of Utah, who is working on the project.

Described in the team's formal report in Thursday's edition of the journal Nature, Falcarius belongs to a group of dinosaurs known as therizinosaurs. The group is a dead-end branch off of an evolutionary path that led from an ancestor shared with Velociraptors to modern birds.

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