A visitor walks between a 15,000-year-old Siberian mammoth skeleton dubbed The

KENOSHA, WIS. ? Somewhere under John Hebior’s 36 acres of cornfields rest the ancient bones of at least one woolly mammoth. But the 76-year-old retiree doesn’t plan to excavate the fossils quite yet.

“I’d like to sell this one first,” he said, gesturing to about 20 boxes containing the carefully packed bones of a mammoth unearthed from those fields 13 years ago.

Unfortunately, turning the cold, hard fossils into cold, hard cash has proved to be a mammoth task. The small pool of potential buyers includes museums and universities, traditionally cash-strapped institutions that can’t easily afford the $100,000 or more he hopes to get for it.

For Hebior, the experience illustrates the challenge of getting full financial value for artifacts whose value is more scientific than commercial.

The Hebior mammoth is about 90 percent intact with minor fragments missing from a foot and elsewhere, said David Overstreet, who helped excavate the fossils in 1994 from Hebior’s farm in the Town of Paris in southeastern Wisconsin.

“It’s an extraordinary specimen because of its completeness,” said Overstreet, 64, an adjunct professor of anthropology at Marquette University in Milwaukee. The specimen is about 13 feet high and 12,500 years old, he said.

The Milwaukee Public Museum approached Hebior about a month ago to inquire about the skeleton, Hebior said, adding that he hopes the museum can acquire the bones to keep them near where they were found. But the museum’s interest is only exploratory, said spokeswoman Ellen Burmeister.

“This is very much a preliminary plan,” she said. “Because of our financial situation now, it would have to be completely sponsored” by a benefactor or corporate donor.

The Field Museum of Natural History in Chicago would be interested, but the museum rarely pays for ancient artifacts, said William Simpson, who manages its collection of fossil vertebrates.

“I wouldn’t say we would never pay, but it would be unusual,” he said. “We like to collect specimens ourselves because we know exactly where they came from, how they were found. That’s just as important as having the fossil.”

Hebior said he didn’t need the tax deduction he could get from donating the skeleton. With four grandchildren entering college in the next five years, he planned to hold out for the best cash offer, he said.

Richard Slaughter, director of the geology museum at the University of Wisconsin-Madison, said his museum is lucky to afford its full-time staff of one, much less to procure “all-star specimens” such as the Hebior mammoth.

Placing a dollar value on fossils is dicey because the real value is whatever the market will bear, said Dan Damrow, a commercial fossil supplier in Mosinee, Wis. He estimated the Hebior mammoth would fetch $150,000 to $250,000, though he said the market had become saturated in recent years after Russia loosened restrictions on sales of its abundant mammoth fossils from Siberia.