A Longview man was banned Friday from entering National Park Service land for one year after digging up the fossilized skull of a hog-like mammal that roamed eastern Oregon 20 million years before humans.

David L. Wixon, 48, also must pay $4,500 in restitution for the misdemeanor crime of depredation of government property, said Assistant U.S. Attorney Neil J. Evans.

An off-duty interpretive ranger at the

spotted Wixon hacking away with a rock hammer at the site on May 6, 2007, and confronted him, according to court records.

Wixon told the ranger he was collecting fossils to give a talk to Boy Scouts, Evans said. But she was skeptical, snapped a photo and took down his license plate.

Federal law enforcement officers investigated. They searched Wixon's home and confronted him about his unauthorized dig. Their suspect eventually returned the skull of an oreodont, a stout hooved creature that vanished from the Earth about 4 million years ago.

The skull was valued at less than $1,000, said Evans, but the loss to humankind was immeasurable.

"The damage to research and the study of this particular skull and the fossil beds -- they've been damaged well beyond the market value of some skull," he said.

The theft was scarcely a piece of petrified wood or leaf imprint, said James F. Hammett, the superintendent of the fossil beds. "Every skull of this type contains vital information regarding the history of the earth," Hammett wrote in a letter to U.S. Magistrate Judge Paul Papak.

"When the skulls like the one Mr. Wixon stole are removed from the monument," he wrote, "the scientific information -- those clues to the ancient past -- are stolen too."

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