Sarah Horgen delicately removed the cloth cover from a large mammoth tooth and set one of her latest excavated artifacts onto the table.

“Finds like this don’t come around every day,” she said.

She and other University of Iowa researchers are preparing to reveal artifacts and other finds from their Oskaloosa excavation project to uncover mammoth bones.

On Wednesday evening, some of the fossils from the UI-led excavation were presented to the public as a part of the UI Explorers Series and in tribute to National Fossil Day. Roughly 40 community members crammed into the small Biosphere Hub in the Museum of Natural History.

Horgen is the educational and outreach coordinator for the museum.

“The more we dig, the more complex we discover it is,” she said.

Landowners in Oskaloosa found the bones in 2010 and took them to the UI, where researchers concluded they were mammoth bones. More fossilized remains were discovered shortly after, and the landowners asked for assistance from UI officials in April to help excavate the bones. The landowner is retaining the bones, allowing the UI to excavate and study them.

The UI research team announced on Sept> 14 the discovery of two separate mammoth species at the site. One of the mammoths is the well-known woolly mammoth, and the other is a Columbian mammoth. The animals are estimated to be between 10,000 and 12,000 years old.

An exact date has yet to be established, but UI Professor Emeritus of geoscience Holmes Semken said researchers will date the bones using radio carbon dating.

“We will use radio carbon dating first on the bone,” he said, noting that researchers will use plant matter around the bone to establish a date. “We’ll be able to date the flora, and we’ll be able to date the bone.”

The public had the opportunity to see various fossilized bones from mammoths discovered across the state that were donated by the UI Paleontology Repository for the event along with a few samples of the finds in Oskaloosa. The fossils from various mammoths across the state consisted of a humerus and vertebra from a baby mammoth along with a tooth and a tusk.

Tiffany Adrain, the collections manager at the UI Paleontology Repository, said once the fossilized bones are removed from the ground, they immediately become very fragile.

“[Researchers are] taking the bones back to the museum’s lab to stabilize them and make sure they don’t fall to pieces,” Adrain said. “You take them out of the ground, and they are instantly fragile; they can fall apart in weeks.”

Horgen said the site is yielding new finds with a higher concentration of bones being found the farther they work from the initial excavation.

“We think we are getting closer to the primary deposit,” she said. “The bone deposit is getting higher as we go back.”

The Columbian mammoth has been found as far north as Alaska and as far south as Central America, being the biggest species and having the longest tusks. The woolly mammoth is known for its hairy coat and curved tusks. It ranged from northern Europe, across Siberia, and into North America. Both species became extinct roughly 11,000 years ago, when the Ice Age ended.

The UI Museum of Natural History is leading the excavation project near Oskaloosa with the Geoscience Department, the College of Engineering, and the Anthropology Department. The UI is also partnering with Iowa State University, William Penn University, and the Office of the State Archaeologist as well.

Volunteers have made this project possible. Horgen has a list of 30 to 40 volunteers waiting to go back to out to the site to help with the excavation.

“We’ve been really grateful for the community involvement,” said John Logsdon, the director of UI Pentacrest Museums.