The Dinosaur That Gave Up Meat

Scientists in the US have discovered a mass graveyard of feathered dinosaurs with teeth that hint at vegetarian appetites.

The excavation of what may be thousands of fossil remains could provide clues about how meat-eating members of the velociraptor family - the predators in Jurassic Park - evolved into herbivores, researchers report in Nature today.

The species, found in Utah and named Falcarius utahensis, dates from the early Cretaceous period 125m years ago.

It ran on two legs, was 1.3 metres (4ft 6in) tall, measured four metres from tip to tail and had 10cm (4in) talons. Nobody knows whether it ate meat, vegetables or both. But its teeth tell a story of vegetarian tendencies.

James Kirkland of the Utah Geological Survey said: "Falcarius shows the beginning of features we now 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."

So far the scientists have collected 1,700 bones, enough to reconstruct 90% of Falcarius, and conclude that it was one of a group of dinosaurs known as therizinosaurs, in turn members of a bigger group called maniraptorans. This group includes the velociraptors. Modern birds evolved from maniraptors. No feathers have been found but feathers or proto-feathers have been discovered on close relatives in China, and the guess is that the Utah finds would have had similarly shaggy, hair-like quills.

Falcarius - the name means sickle-maker, because later plant-eating therizinosaurs had one-metre-long sickle claws - is unequivocal evidence that herbivores evolved from velociraptor-like ancestors, according to Lindsay Zanno, a co-author of the report.

It had leaf-shaped teeth rather than the triangular, blade-like serrated teeth of most of its relations.

One scientist called the discovery "evolution caught in the act".

The graveyard was discovered in east-central Utah, south of a town called Green River. The site was spotted by a commercial fossil collector, later convicted of fossil theft, who led scientists to it.

Dr Kirkland estimates that thousands of dinosaurs are preserved at the dig. Nobody knows why so many creatures died in the same place: drought, volcanic eruption, fire and mass poisoning have been suggested.

Scott Sampson of the Utah Museum of Natural History said:"This little beast is a missing link between small-bodied predatory dinosaurs and the highly specialised and bizarre plant-eating therizinosaurs."