First with shovels and chisels, then with sweeps of whisk brooms and soft-bristled paint brushes, volunteers Saturday loosened the sandstone that protected the bones of an American mastodon for at least three million years.
The bones, spotted last month by teen motorcyclists Derek Prosser and Dustin Turner in the Pine Nut Mountains southeast of Gardnerville, were being removed to preserve them from possible vandalism on the Bureau of Land Management-controlled property.
After an hour of shoveling removed loose sand from the foreleg bones, volunteers like Ron Jones and his 14-year-old son, Zach, of Sparks, turned to the smaller tools to separate the soft sandstone from the fossilized remains revealed in the hillside.
The sandstone, formed by sediment deposits in ancient river beds, contains substantial amounts of broken fossilized remains of camels, horses, mastodons and even saber-toothed cats, according to Tom Lugaski, curator of the W.M. Keck Museum at the University of Nevada, Reno.
"But finding larger bones as intact as this is kind of like hitting Megabucks," the bearded Lugaski said as he displayed a chunk of the mastodon's skull that included part of a nasal cavity. He also showed fossilized tooth fragments found in the area Saturday morning that probably were from an ancient horse or camel.
Lugaski said there was no way to tell how much of the mastodon will be recovered from the site except by excavation.
"From the angle of the leg bones into the hillside, it may be that the skeleton extends back into the hill," he said. "If we find indications there is more in there, like a backbone, we'll re-evaluate the situation and may decide to bring a backhoe in to help uncover the rest."
As the cleaning process progressed down one foreleg bone, smaller fossils that could have been toe or foot bones were uncovered, possibly indicating that much of the skeleton was still together.
There is no way to be certain how this particular mastodon died, he said. Finding the fossils of an individual large mammal usually indicated it died of old age or was killed by a predator. Finding a group of one kind of skeletons can suggest they were killed by some disaster, possibly from a flood or volcanic eruption.
Tom Muntean, a UNR geology student working on his masters degree, had already been studying the sedimentary patterns of the area as his masters project when the mastodon fossils were found. He said their approximate age was determined through several evaluations, including the presence of specific isotopes of argon gas in the glassy volcanic ash in the sediment.
Mastodons, related to modern elephants, inhabited North America between 3.875 million and 10,000 years ago. They stood 8-10 feet tall at the shoulder and fed on herbs, shrubs and trees. They were about half the height of mammoths, a skeleton of which is featured at the Nevada State Museum in Carson City. Theories about why the mastodons, camels and horses disappeared from the continent about 10,000 years ago include hunting by early human inhabitants or environmental causes due to climate changes.
BLM historical archeologist Gary Bowyer praised Prosser, who visited the site Saturday, and Turner for reporting their find. Archeological and cultural materials on federally controlled lands are protected by federal law and there are penalties for disturbing or removing them. Bowyer said the mastodon discovery provides an opportunity to inform the public to report such finds immediately so they can be documented and studied.
The fossils recovered from the site so far would not have any significant cash value to collectors because they are incomplete, Lugaski said, but are important to researchers trying to understand where animal populations once existed.
The fossils are being taken to UNR where they will be cleaned, preserved, studied and stored.