Pacific Mastodon Tooth Unearthed in San Mateo County Creek

A fossilized tooth belonging to a Pacific mastodon has been recovered from a wooded creek in a mountainous stretch of the San Francisco Bay Area, after a geomorphologist working on a habitat restoration project spotted it earlier this year.

Brigid Lynch, a geomorphologist at Balance Hydrologics, was surveying a creek in a Midpeninsula Regional Open Space District preserve in San Mateo County when she noticed an object that stood out from the surrounding rocks. The tooth was resting in the water, partly submerged.

"I keep joking it wasn't hard to find," Lynch said Friday. "It was just sitting there in the middle of the creek, halfway in, half out of the water."

The discovery occurred during work tied to a restoration project for the threatened California red-legged frog. The district, which manages more than 70,000 acres across the Santa Cruz Mountains region, announced the find this week.

The fossil has been donated to Stanford University's Doerr School of Sustainability. Chrissy Garcia, curator and manager of the school's specimen collections, described the tooth as exceptionally well preserved, with both the crown and the root intact.

"It's in great condition," Garcia said. "So we've got both the crown and the root of the fossil. You can even see root canal."

She added that the specimen's quality and local origin made it a notable acquisition. The tooth measures about 9 inches (23 centimeters) long.

Ron Tykoski, vice president of science and curator of vertebrate paleontology at the Perot Museum of Nature and Science in Dallas, said mastodon fossils surface with some regularity depending on the region. Multiple mastodon species roamed North America for millions of years until roughly 10,000 to 12,000 years ago, he noted.

"The way this was found is actually the way a lot of specimens are found, just somebody who happened to be in the right place," Tykoski said.

Garcia said the next steps will likely include efforts to determine the fossil's exact age and the creation of a 3D copy for the Midpeninsula Regional Open Space District. The district plans to use the replica for public outreach and education.

Ryan McCauley, a spokesperson for the district, said the find underscores the value of preserving open spaces and habitats.

"That this tooth, that this molar, was found in the context of trying to protect the habitat and save another species from potentially going extinct I think really just drives home the point of why it's so important to care for these open spaces and these natural lands," he said.