HOT SPRINGS - Joanne Bugel is happy to be the Earthwatch volunteer who uncovered the 115th tusk at the Mammoth Site and moved the popular Hot Springs tourist site's mammoth tally to 58.

But it's the smaller, still unknown bone she found on Thursday that really warmed her amateur archeologist's heart.

"I prefer the small bones. I like the mystery of them," said Bugel, a New Jersey nurse and self-described science nerd.

Bugel and 11 other volunteers will wrap up a two-week excavation on Saturday, the last of two Earthwatch digs for the summer season. This group has been a particularly productive bunch, said crew chief Don Morris.

"They're finding things faster than I can keep up with the paperwork," said Morris, a retired National Park Service archeologist. Bones unearthed by 2008 Earthwatch volunteers include: three tusks, a tooth, a patella, six ribs, a fibula, four vertebra and assorted other bones.

Neteal Graves, 18, of Kaycee, Wyo., also unearthed some coprolite - otherwise known as petrified mammoth poop.

Graves' prehistoric dung may not have been as impressive as the two tusks and an intervertebral disc that the father-son team of John and Austin Anderson got credit for finding, but Graves was thrilled by it. "At first I thought it was a rock. Then I thought it was a bone I broke, so when I found out what it was, I was still happy with it," she said.

Graves has the Mammoth Site in her bloodline. In 1974, her mother, Cheri Graves, was a college student who came with Prof. Larry Agenbroad to the site of a sinkhole that would later become the world's largest mammoth research facility. Agenbroad, the site director and principal investigator, is retired now from Northern Arizona University and his former student's daughter is heading off to Augustana College this fall to study archeology and paleontology.

The Andersons, of Alabama, won their Earthwatch expedition from the cable television show Animal Planet. Others pay more than $2,000 for the privilege of a two-week treasure hunt spent digging in hard clay with trowels and dental picks and brushes.

"It's thrilling," said Vee Lamb of discovering a new bone. The Pennsylvanian volunteer is on her 20th Mammoth Site dig. "Yours are the first human eyes to see these things - ever."

Morris estimates that 100 or more mammoths may eventually be found in the sinkhole "There's still 30 feet of pay dirt below us, enough to keep us busy digging for another 30 years, at least," he said.

As he brushed away dirt from what will probably be a pelvic bone, Austin Anderson, 16, joked that it might prove to be the dig's first female mammoth.

The first 58 mammoths have all been identified as male, most of them young animals between 17 and 25 years of age that got trapped in the sinkhole in a short period of time 26,000 years ago, Morris said. The adolescent mammoths, kicked out of the herd as they reached sexual maturity, probably didn't know enough to avoid the dangerous sinkhole, he said.

Only a small portion of 115th tusk is visible right now and it will be years before it is properly excavated. But its discovery moves scientists a little closer to the final tally, and it ensures that tourists like 6-year-old Emily Raskins of Minneapolis will keep coming back to the ever-evolving in-situ display of mammoth bones.

On Thursday, Emily and her parents were among the 1,000 or so people who have been visiting the site daily this summer.

"It's a long-term project," Morris said. "We're leaving a little for our grandchildren to unearth."

To learn more about becoming an Earthwatch Excavation volunteer at the Mammoth Site in Hot Springs, call Earthwatch at 800-776-0188

Contact Mary Garrigan at 394-8424 or mary.garrigan@rapidcityjournal.com