This photo provided by Midpeninsula Regional Open Space District shows the fossilized tooth of a Pacific mastodon, June 10, 2026, at their headquarters in Los Altos, Calif. (Midpeninsula Regional Open Space District via AP)
Brigid Lynch was working along a wooded creek in a mountainous part of the San Francisco Bay Area when something that didn’t look like the rocks she’d been studying caught her eye. It turned out to be the fossilized tooth of a Pacific mastodon.
“I keep joking it wasn’t hard to find,” Lynch, a geomorphologist at Balance Hydrologics, said Friday. “It was just sitting there in the middle of the creek, halfway in, half out of the water.”
Lynch made the discovery earlier this year while working on a habitat restoration project for the threatened California red-legged frog in a Midpeninsula Regional Open Space District preserve in San Mateo County. The public land management agency that preserves over 70,000 acres of land in the Santa Cruz Mountains region announced the find this week. The fossil has been donated to Stanford University’s Doerr School of Sustainability.
“It’s in great condition,” said Chrissy Garcia, curator and manager of Doerr School of Sustainability’s specimen collections. “So we’ve got both the crown and the root of the fossil. You can even see root canal.”
