What looked like a strange rock in a Bay Area creek turned out to be something much older and rarer.
A scientist working in San Mateo County discovered an intact mastodon tooth during a field survey at a Midpeninsula Regional Open Space District preserve, officials said in a news release announcing the find.
The fossilized molar was later identified as belonging to an adult Pacific mastodon, an extinct relative of modern elephants that once roamed parts of California and the western United States.
Researchers believe the tooth could be about 10,000 years old.
Geomorphologist Brigid Lynch made the discovery while surveying the creek as part of a habitat restoration project.
"As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this," Lynch said.
Paleontologists who examined the fossil said it was unusually well preserved.
"The tooth itself is in immaculate condition," Wayne Thompson, a paleontologist and owner of Pacific Paleontology, said.
Pacific mastodons lived during the Pleistocene Epoch, which began roughly 2.5 million years ago, and disappeared about 11,700 years ago.
The tooth has since been donated to Stanford University's Doerr School of Sustainability, where researchers plan to carbon-date it to get a more precise estimate of its age.
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Scientists also plan to create a 3D scan of the fossil and make a replica for educational use.
Officials said the discovery offers a glimpse of the animals that once lived in what is now Northern California's Bay Area.
"Fossils are our only opportunity to see into past biodiversity," Christine Garcia, curator and manager of Stanford's Geoscience Specimen Collection, said.
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