A paleontologist has identified an exceptionally well-preserved molar from an adult Pacific mastodon, a rare Ice Age relic discovered in a creek bed in San Mateo County, California. The tooth, estimated to be more than 10,000 years old, is considered the most complete specimen of its kind found in the region.
The discovery was made over the summer by Brigid Lynch, a geomorphologist conducting fieldwork for a project aimed at supporting the threatened California red-legged frog. Lynch initially mistook the object for an unusually shaped rock.
Paleontologists later confirmed the find as an intact Pacific mastodon molar. Wayne Thompson, a paleontologist with Pacific Paleontology, described the tooth as being in immaculate condition and called it the most spectacular mastodon molar he has ever seen. The find was announced by the Midpeninsula Regional Open Space District (Midpen).
Pacific mastodons, relatives of modern elephants, roamed parts of the West, including California, during the Pleistocene epoch, which spanned from approximately 2.5 million years ago to about 11,700 years ago. Unlike mammoths, which grazed on grasses, mastodons were browsers, feeding on leaves, shoots, and fruits from woody plants.
Scientists believe the discovery could provide valuable information about the Pacific mastodon, a distinct species officially recognized only in 2019. This subspecies is distinguished from its American counterpart by features such as narrower teeth and thicker leg bones. Much about the ancient creature's life and behavior remains unknown.
In July, the fossilized tooth was donated to Stanford University's Doerr School of Sustainability for further study. Researchers plan to carbon-date the tooth for an exact age determination and create a 3D scan and replica for public education. Christine Garcia, curator and manager of Stanford's Geoscience Specimen Collection, emphasized the importance of fossils in understanding past biodiversity and informing future conservation efforts.
This is not the first Pacific mastodon tooth found in the area. In 2023, a woman discovered a similar fossilized tooth on Rio Del Mar State Beach near Santa Cruz. That discovery, initially thought to be driftwood, was identified by Wayne Thompson and later donated to the Santa Cruz Museum’s artifact collection. At the time, Thompson noted it was one of only three known Pacific mastodon specimens from the region and suggested it provided evidence of lower sea levels during fossilization, allowing such creatures to traverse areas now separated by water.