A geomorphologist conducting a habitat restoration survey in the San Mateo County hills has uncovered a remarkably preserved fossilized tooth belonging to a Pacific mastodon, an extinct relative of modern elephants that roamed the region during the Ice Age.
The discovery was made by Brigid Lynch, a geomorphologist with Balance Hydrologics, while performing fieldwork for the Midpeninsula Regional Open Space District (Midpen). The fossil, identified as an adult molar, was found in a creek bed within a Midpen preserve, though the specific location has not been disclosed. Officials confirmed the tooth is at least 10,000 years old and represents a significant find for paleontologists studying the distinct Pacific mastodon species.
Pacific mastodons, recognized as a separate species from their eastern counterparts since 2019, had narrower teeth, thicker leg bones, and different tusks. Their range extended across California, Oregon, the northern Rocky Mountains, and parts of Mexico. The species went extinct approximately 11,700 years ago at the end of the Pleistocene epoch.
Paleontologists have praised the fossil’s condition. Wayne Thompson, a paleontologist and owner of Pacific Paleontology, described the tooth as "in immaculate condition" and noted it as the most complete mastodon molar found in the region. Researchers at Stanford University’s Doerr School of Sustainability plan to conduct carbon dating to determine the tooth’s precise age.
Midpen, which manages over 70,000 acres of open space in the Bay Area, announced the discovery in a news release but did not specify when the fossil was found. The agency did not respond to requests for additional details.
The find occurred during a survey supporting the threatened California red-legged frog, a federally protected species. Lynch, who has prior field experience, stated in a Midpen news release that the discovery was unlike anything she had encountered before.
Pacific mastodons, which coexisted with saber-toothed cats and dire wolves, were massive, hairy creatures adapted to the lush landscapes of the Ice Age. Their extinction marked the end of an era that shaped the biodiversity of North America. This fossil provides a tangible link to that prehistoric world, offering researchers a new piece of evidence to reconstruct the species’ behavior, diet, and habitat preferences.
While the exact creek where the tooth was found remains undisclosed, Midpen officials emphasized the importance of preserving such discoveries within protected open spaces. The agency’s role in maintaining these habitats ensures that future generations may uncover similar remnants of the past.