10,000-year-old fossilized mastodon found in creek
The fossil was found in exceptionally well-preserved condition, scientists said.
A fossilized Pacific mastodon tooth that scientists say is at least 10,000 years old and in “immaculate condition” was discovered recently in in a creek bed in California, according to local officials.
The "exceptionally preserved fossilized tooth" was discovered during field surveys for a habitat enhancement project in a Midpeninsula (Midpen) Regional Open Space District preserve in San Mateo County, California, according to a Midpen press release.
“It's the most complete mastodon molar from our area, and the most spectacular mastodon molar that I've ever seen,” Wayne Thompson, a paleontologist and owner of the environmental planning and management firm Pacific Paleontology, stated in the press release. “I had chills and shivers up and down my spine.”
The fossil was initially believed to be an oddly shaped rock before paleontologists confirmed it was an intact molar from an adult Pacific mastodon, according to the press release.
The tooth is about 8.5 inches long, 7 inches deep and 3 inches wide, according to Midpen.
“As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this,” said Brigid Lynch, who discovered the tooth.
The Pacific mastodon was a massive herbivore that roamed California, Oregon, the northern Rocky Mountains and parts of Mexico in the Pleistocene epoch, from about 2.5 million years ago until 11,700 years ago, when the animals went extinct, according to the press release. It differs from the more well-known American mastodon by featuring narrower teeth, thicker leg bones and different tusks, the press release said.
The mastodon resembles the woolly mammoth but differs in several ways, including featuring molars that are suited for crushing twigs and other vegetation. Both of the large mammals are distant relatives of the elephant and existed in similar regions and time periods.
The mastodon tooth was donated to the Doerr School of Sustainability at Stanford University, where researchers plan to determine its exact age through carbon dating and will create a 3D scan of it, the press release said.
“We can study fossils to better understand Earth’s past, past wildlife and the ecosystem they were a part of, and to help us make better predictions and better decisions about how to help our ecosystems and biodiversity thrive into the future,” Christine Garcia, curator and manager of the Geoscience Specimen Collection at Stanford University, stated in the Midpen press release.
Researchers have used DNA from mastodon fossils to discover the mammal was far more genetically diverse than previously known and that it had migrated long distances in response to a shifting climate, according to a 2025 study published in the journal Science Advances.
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