Directions to the Allen L. Cook Spring Creek Preserve and prospecting locations within it are somewhat vague.

This is done on purpose because of the real risk of fossil theft.

Edward McCord, University of Pittsburgh Honors College Program director and preserve coordinator, asked that specific information about routes, geologic locations and paleontological sites not be used.

"Some articles about the preserve have termed it the 'best since Como Bluff,' and that may have overblown it, but there have been historic instances of people raiding dinosaur digs and we are concerned," said Mandela Lyon, a paleobiologist and co-instructor for this summer's University of Pittsburgh field course.

Como Bluff is the nearby fossil-rich site north of Medicine Bow, Wyo. that between the 1860s and 1890s yielded such finds as the Diplodocus carnegii, bones better known today as the Carnegie Museum of Natural History's "Dippy."

Fossil smuggling from Russia, China and Australia is widespread. Because of the likelihood of theft, important finds in Australia are protected and often kept secret. One such middle of the night theft involved the use of jackhammers to take a stegosaurus footprint.

Between 1995 and 1998, the National Park Service identified 721 documented incidents of paleontological resource theft or vandalism, many involving multiple specimens. The number of thefts has risen as prices have gone up.

In 1991, an Allosaurus skeleton was stolen from federal Bureau of Land Management land southeast of Fremont Junction, Utah and sold to a Japanese buyer for $400,000. A BLM official said of the theft, "Because it was crudely collected, we have lost any chance to study the way the skeleton lay in the ground, how it was buried, what happened to it after death, and other plants or animals that may have been buried with it. We have lost a priceless piece of America's natural heritage."

"We're not trying to keep this a secret or be too guarded, but we are trying to preserve material for future educational and research purposes," Ms. Lyon said. "We're just being cautious."