GARDINER, MONT. — Court filings made public on Monday reference a treasure trove of one-of-a-kind artifacts described as an “American Pompeii” at the center of a legal dispute between the federal government and a Montana rancher, lifting the veil on a long-secret research project at the edge of Yellowstone National Park.

At stake is ownership of hundreds or perhaps thousands of well-preserved animal remains, including fossils of long-extinct mammals, as well as what researchers believe are among the earliest tools and ceremonial objects ever found in the region. Human remains may also be present at the site, based on motions filed on behalf of tribal interests.

Government and university archaeologists have been toiling in secret for the last few years to unearth, preserve, catalog and study the contents of a large cave along the northern boundary of Yellowstone Park. Exactly how much of the cave lies within Yellowstone and how much is on a private ranch is central to a federal lawsuit that will determine whether its contents wind up in public or private hands.

But only broad strokes of the historic find have been outlined in court documents, and both sides—along with a federal judge—are declining to provide key details, citing concerns about keeping the site safe and secure from curious hikers or treasure hunters.

The lack of solid information in the case has given rise to rumors and speculation about everything from mythical creatures to alien technology, said one independent archaeologist not connected to the dig.

“I’ve gotten calls about pieces of a flying saucer being found, as well as one gentleman who claimed to have a Yeti toe” from the site, said Leonard Gutveldt, an archaeologist with the University of Montana in Missoula.

Gutveldt said he has been in touch with locals around Gardiner, Mont. about the site for the past year, as well as with researchers who claim to have worked in the cave. But independently verifying information has proven difficult, he said.

After reviewing newly released court filings and other documents made available this week, Gutveldt said the site “could prove to be more amazing than anything else ever found in Yellowstone, from Old Faithful to the Grand Canyon of the Yellowstone.”

“This looks very much like what I could only describe as an American Pompeii,” said Gutveldt. The cave, referred to in court documents as Bone Creek Cavern, appears to hold specimens as plentiful and well-preserved as the ancient Italian city of Pompeii, buried in ash when volcanic Mt. Vesuvius erupted nearly 2,000 years ago.

“But where Pompeii was a single event, Bone Creek Cavern appears to have been subject to a series of floods and other unique natural process that trapped and preserved animals and people in many separate incidents over thousands of years,” Gutveldt said.

Court documents allude to the remains of long-extinct ice age mammals like the North American lion and the American cheetah, as well as projectile points, pottery shards and “what may be the remains of human adults and children.”

Sprawling complex

Based on a lawsuit filed in U.S. District Court in Butte on behalf of a Montana rancher identified only as “John Doe,” Bone Creek Cavern straddles the boundary between Yellowstone and private land owned by Doe. The sprawling complex could stretch underground for a half-mile or more, according to court records.

Judge Garland issued a motion last week making public some of the filings in Doe’s lawsuit, while keeping some documents under seal and partially redacting others. The initial complaint, much of which was heavily redacted by the court, was filed in August 2012. It appears to center around access to the site itself, as well as ownership of items found inside.

Janet Kersten-Hoff, a Billings, Mont. attorney representing Doe, said the rancher’s nephew discovered the cave in May 2010 after a spring flood and series of tremors caused a basalt formation to split away from a rock cliff.

“After discovering the cave, my client worked diligently to secure it and ensure its contents would go undisturbed. But as with so many other issues across the West, the federal government decided it needed to get involved, despite having no standing,” Kersten-Hoff said. “It’s yet another case of classic federal over-reach.”

Federal attorneys contend in court documents that Doe was “looting the cave in secret,” before its discovery was known to park officials, and question whether “countless irreplaceable treasures may already have been spirited away, never to be seen.”

Kersten-Hoff maintains that Doe used GPS readings and “other careful measurements” to limit his activities to those portions of the cave that were “entirely on his own private property,” and that federal authorities have launched a “witch hunt” meant to intimidate and silence him.

“If he had done something he shouldn’t have, my client would have been charged with a crime, and he hasn’t been,” she said. “This is a case of Big Brother wanting to bully all the kids on the playground into giving up all their marbles.”

Yellowstone spokesman Stan Thatch said that shortly after park officials heard about Bone Creek Cavern in summer 2010, they began confidential discussions with Doe to determine the best way to preserve and document its contents.

“Both the private party and Yellowstone staff agreed that it was in everyone’s best interest not to publicly disclose details about this very sensitive site,” Thatch said. “It is not at all uncommon for researchers to take a low-profile approach with these kinds of situations.”

Both sides agreed to let government and university archaeologists work the site as part of an initial survey aimed at determining the extent of the find, and to map the entire complex. Because the cave’s lone entrance can only be reached from Doe’s property, an access agreement was drafted allowing both sides certain rights, according to court filings.

Details withheld

Specific details on the cave’s size and location were not revealed in court documents. Judge Garland stated in a March 17 order that no parties may discuss “any element of the case that might reveal the cave’s contents or its location,” including Doe’s identity or geographic specifics of the surrounding area. “Bone Creek” appears to be a euphemistic place name used informally by researchers, and does not refer to any specific drainage in the area.

“It would be a tragedy if a site like this were to be plundered or damaged by looters or careless wanderers,” Gutveldt said.

Thatch said the cave’s entrance is securely locked, and a range of “remote monitoring equipment is in place that will let us know if someone is trespassing.”

But whether anyone will be entering the cave anytime soon is the most pressing issue outlined in court documents filed on behalf of Doe in a string of back-and-forth filings going back more than two years.

Kersten-Hoff successfully argued in motions unsealed this week that the dispute over Bone Creek Cavern should be public, because the actions of the National Park Service amount to a “taking” of Doe’s private property, or at least an unreasonable restriction on how he may use his own land.

Gutveldt said similar archaeological sites in Wyoming hint at what might lie undiscovered in Bone Creek Cavern.

Natural Trap Cave, located on federal land in the Bighorn Mountains, was opened to researchers last summer, and has yielded fossils of ancient bears, mammoths and camels.

Mummy Cave, located in the Shoshone National Forest just east of Yellowstone, was used by native peoples dating back 9,000 years, Gutveldt said. Researchers there found dozens of stratified layers yielding hides, bone, wood, feathers and even mummified human remains.

“Based on the gossip and rumors I’ve been hearing about Big Bone Cavern, along with what I’ve read in the court papers, this could make both of those sites pale in comparison,” Gutveldt said. “I’m hoping they can work a deal to make whatever they find available to the public.”

Other more outlandish gossip and rumors continue to swirl around the cave, including one popular local legend that it held “alien technology.” That idea has been fueled by a widely circulated court document listing sealed legal motions filed by attorneys for the National Aeronautics and Space Administration, the U.S. Department of Energy, Tesla Motors and Apple Computer, among others.

“Because we’ve only seen the names of those entities, but not their actual filings, I can’t imagine why they’d be interested,” Gutveldt said. “It is very much out of the ordinary.”

Thatch said he had no information on the unusual court filings, while Kersten-Hoff would say only that her client “has been in touch with a lot of people about some of the more unusual items located on his private property.”

Kersten-Hoff said her client “wasn’t dead-set against a deal” that could see all of the cave’s contents placed in public hands, “but he has to be compensated fairly, and treated with some measure of appropriate respect” by federal authorities.

Gutveldt is still awaiting results from an analysis of the purported Yeti toe.

Contact Ruffin Prevost at 307-213-9818 or ruffin@yellowstonegate.com.

UPDATE: Thanks to everyone who enjoyed this year’s April Fools joke, and especially to those friends on Twitter who helped spread #YetiToe.