Government plans to more than double the size of Petrified Forest National Park appear to be in jeopardy because Congress has failed to come up with the cash to buy surrounding properties.

The upshot: An irreplaceable treasure of dinosaur bones and Indian ruins may be lost as ranchers sell off their properties for subdivision and development.

And Petrified Forest is not alone. A study to be released April 8 by the non-profit National Parks Conservation Association, says 56 federal historic and recreation sites "could lose land inside their borders to developers this year." Others on the list range from Gettysburg National Military Park near Philadelphia to Golden Gate National Recreation Area in San Francisco.

Petrified Forest, among Arizona's most recognizable national parks, sprawls over nearly 100,000 acres of unique geological turf between Heber and Holbrook. Scientists say adjacent ranches are peppered with relics that provide windows into prehistoric eras.

After hearing testimony from paleontologists and archaeologists in 2004, Congress agreed to more than double the park's size, authorizing a 125,000-acre expansion. The Park Service even put dotted lines on maps to show the new boundaries.

But one year went by, then another and another. The government offered no money to ranchers. Federal land-exchange proposals flopped. And now one of the most critical parcels is up for sale.

Twin Buttes Ranch is a veritable museum of dinosaur skeletons and Pueblo ruins preserved by a freakish convergence of geography and natural history.

Owner Mike Fitzgerald, 57, who doesn't collect bones or bowls, said he supported government plans to acquire his land. Cattle prices had fallen, and drought had wiped out his herd. So he sat back and waited for a buyout that would fund his retirement.

"I have a lot more petroglyphs on my place than the park has," Fitzgerald noted. "We had a ranger come through here and he says, 'Gosh, you've got enough for two national parks.' "

Fitzgerald said he thought his lands would be purchased within a few years, but nothing happened. Last month, he quit waiting and put a "For Sale" sign on Twin Buttes Ranch, with an asking price of $10.5 million.

Even his Scottsdale real-estate agent, Brett Rubin, frets that the public is about to lose a priceless resource.

"It's so important, but the Park Service can't figure a way to pay for it or trade for it," Rubin said. "And if somebody wants to turn this into 40-acre ranchettes, the government is screwed."

Fitzgerald said he'd like to be a good steward. But if a developer comes along with cash, "I'd take it. I feel like the government had their chance."

Glenna Vijil, a realty officer with the National Park Service, said only one small tract of land has been acquired since expansion was approved. She acknowledged that prices have risen dramatically in three years, and subdivision could drive them higher. (Unlike on public land, private owners can dig for artifacts and develop the properties except where burial sites exist.)

Vijil said the fund crunch is a chronic problem at America's national parks. Because Petrified Forest is now among the top five on a priority list, she added, "I'm optimistic that we will get funding . . . even if it's just a start."

Calculating the total price of expansion is guesswork without a recent appraisal. Vijil puts the figure at about $18 million to $20 million, with the largest tracts costing $150 per acre. Fitzgerald figures his ranch, mostly rolling grassland zoned for agriculture, is worth $300 per acre.

Fitzgerald said he got the Twin Buttes, oddly enough, as part of a federal land exchange in 1986. At that time, his family owned a ranch near the Painted Desert. The government was trying to resolve a turf dispute between the Hopi and Navajo tribes and needed land to make the deal work. So the Fitzgeralds swapped for a giant tract east of Holbrook, only to have the government want it back two decades later.

Twin Buttes covers 60 square miles, including some lease lands. David Gillette, curator of vertebrate paleontology at the Museum of Northern Arizona, testified during a 2004 congressional hearing that the Triassic Period, about 220 million years ago, is frozen in time here, along with centuries-old Pueblo ruins.

Gillette told lawmakers that the Petrified Forest holds "a bonanza of secrets" that may help in dealing with present-day environmental problems.

"Gut-wrenching stories of predator-prey interactions, floods that carried trees as large as giant redwoods into log jams, and the humble beginnings of our modern world can be pried from the rocks. . . . We cannot afford to lose these stories or the ability to share them," Gillette testified.

Fitzgerald said he's just an old cowpoke and not really into antiquities. But neighbors keep pottery and relics in their homes; his 12-year-old son is a gatherer of arrowheads and fossils. So he appreciates the fascination.

Some areas around the park have already been vandalized, he added, and others have been developed.

"For years, I've watched this country be subdivided and just the degradation of the land," Fitzgerald said.

He said there was talk several years ago of trading Twin Buttes for Bureau of Land Management property in southern Arizona. That deal fell apart, and nothing followed.

David Nimkin, Southwest regional director for the non-profit National Parks Conservation Association, said the story is similar for other giant parcels around Petrified Forest.

"The federal government authorized expansion but didn't appropriate any funds," Nimkin said.

Rubin said the Park Service can't even afford to pay for a new appraisal, so "the chances of anything happening with the government are slim and none."

He tried to attract interest from the Nature Conservancy and other environmental groups, to no avail. Now, Rubin said, he's dealing with a couple of private developers.

Fitzgerald said he has grown skeptical - eager to sell but tired of false promises.

"I'm like the donkey who's been chasing the carrot too long," he added, "just sitting back on my haunches."