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)
A fossilized tooth of a Pacific mastodon, left, is displayed during an interview in the Stanford Doerr School of Sustainability, Tuesday, Sept. 15, 2026, in Palo Alto, Calif. (AP Photo/Jeff Chiu)
A fossilized tooth of a Pacific mastodon, left, is displayed during an interview in the Stanford Doerr School of Sustainability, Tuesday, Sept. 15, 2026, in Palo Alto, Calif. (AP Photo/Jeff Chiu)
Chrissy Garcia, curator and manager of Stanford Doerr School of Sustainability, specimen collection, gestures toward a fossilized tooth of a Pacific mastodon during an interview, Tuesday, Sept. 15, 2026, in Palo Alto, Calif. (AP Photo/Jeff Chiu)
A fossilized tooth of a Pacific mastodon, left, is displayed during an interview in the Stanford Doerr School of Sustainability, Tuesday, Sept. 15, 2026, in Palo Alto, Calif. (AP Photo/Jeff Chiu)

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.”

Get The Latest News!

Don't miss our top stories and need-to-know news everyday in your inbox.

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.”

“It’s exciting to have a specimen of this quality, and having it be a local find,” she said.

Garcia said the tooth from the Pacific mastodon, an extinct elephantlike species, is about 9 inches (23 centimeters) long.

Article continues after sponsor message

Ron Tykoski, vice president of science and curator of vertebrate paleontology at the Perot Museum of Nature and Science in Dallas, said mastodon fossils “pop up with some degree of frequency, depending on where you live.”

He said there are multiple species of mastodon that roamed for a few million years in North America, up till 10,000 to 12,000 years ago.

“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 that they’ll likely try to determine the exact age of the fossil, and will make a 3D copy to give to the Midpeninsula Regional Open Space District. The district says it will use the copy for public outreach and education.

Ryan McCauley, a spokesperson for the district, said the discovery on land they are preserving helps show the value of protecting 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.

 

More like this:

Japan’s biomass energy boom threatens further deforestation in Indonesia
Sep 13, 2026
Newsom talks climate with world leaders in New York, accuses Trump of abdicating that responsibility
3 days ago
Ugandans plant trees near national park to keep people out of gorillas’ habitat
2 days ago
Climate change made deadly Nepal glacier and rock collapse more likely, according to analysis
Sep 16, 2026
Cheetah cubs at Prague Zoo are doing well after a period of strong storms and their mother’s illness
Yesterday