10,000-year-old mastodon tooth found in this Bay Area creek

LOS ALTOS, Calif. - A recent routine field survey in the Bay Area led to a rare and stunning prehistoric discovery of an intact tooth from the ice age.

It happened in the Midpeninsula Regional Open Space District (Midpen) preserve in San Mateo County as researchers were surveying creeks focused on the threatened California red-legged frog.

Inadvertent discovery 

That’s when Brigid Lynch, an experienced scientist with Berkeley-based environmental consulting firm Balance Hydrologics stumbled upon an object in a creek bed that initially appeared to be "an oddly shaped rock," Midpen shared in a news release announcing the discovery last week. 

Paleontologists examined the rock-like object and later confirmed that it was an exceptional find — an intact molar that belonged to an adult Pacific mastodon.

What they're saying:

"As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this," Lynch was quoted as saying in the news release.

Santa Cruz-based Pacific Paleontology conducted a site geological assessment and was among those involved in the analysis of the specimen.

"It is perhaps the most spectacularly well-preserved mastodon molar We’ve ever seen found locally here in the Bay Area to date," the group shared on Facebook.

Researchers described the tooth as an upper left third molar, noting that it showed minor wear and speculating that it came from a mastodon that was in its early 40s. 

"The tooth itself is in immaculate condition," shared Pacific Paleontology owner Wayne Thompson, who added, "I had chills and shivers up and down my spine."

10,000 years old

The fossilized mastodon tooth is estimated to be about 10,000 years old. 

Dig deeper:

Pacific mastodons were massive herbivores from the Pleistocene epoch spanning 2.5 million years ago until their extinction around 11,700 years ago, according to Midpen.

The ancient mammals are believed to have lived in western North America, primarily ranging across California, Oregon, the northern Rocky Mountains as well as parts of Mexico.   

These prehistoric animals, a distant relative to the modern day elephant, were different from mammoths, which also roamed the region. Mammoths, however, were grazers and fed on grasses, while mastodons’ cone-shaped molar cusps were ideal for a diet that came mostly from trees. 

"Mastodons were considered browsers, using their massive trunks to strip leaves, soft shoots or fruits of high-growing, generally woody plants," the Midpeninsula Regional Open Space District explained. 

‘Same iconic wildlife’

Midpen noted the similarities between the home that once belonged to mastodons and the land and its inhabitants today. 

"These ancient landscapes of what is known now as the San Francisco Bay Area shares many of the same iconic wildlife and plants we see on our trails today," the district wrote. "Tule elk, coyotes  and American badgers likely roamed the valleys inhabited by mastodons and bison-sized  Jefferson’s ground sloths."

The Pacific mastodon is a relatively newly identified species, officially named and recognized by researchers in 2019, according to the scientific journal PeerJ.  

Donated to Stanford

Midpen donated the fossil to Stanford University’s Doerr School of Sustainability. Researchers there plan to conduct further research on the tooth, using carbon dating to determine its exact age, which is expected to yield a depth of information including the regional significance of this species. 

Stanford experts said they are in the early stages of analyzing the specimen but speculated that the fossil is at least 10,000 years old, based on the timing of the species' extinction and other mastodon fossils from the region.

"Determining the age of this particular specimen will allow us to better understand not only the individual animal the tooth came from, but the broader context of our local Bay Area environment and the animals that inhabited it during the Ice Age," Stanford's Geoscience Specimen Collection Curator and Manager Christine Garcia explained to KTVU in an email correspondence.

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Garcia pointed out that discoveries such as the one Lynch made usually happen during major projects that involve massive excavation work.   

"It is quite rare for a mastodon tooth to be inadvertently discovered in this part of the United States," Garcia said, expressing how excited researchers are to add the fossil to Stanford’s paleontology collections. 

Big picture view:

Midpen said the celebrated discovery further validates the work its staff is doing to protect and restore its open space and the wildlife on it. 

District biologist Matt Sharp Chaney said that when considering the earth’s geological time spanning 4.5 billion years or more, the finding puts into perspective that the existence of mastodons was not that long ago.

"That mastodon were out here in the same landscape that we’re in today," Chaney said, "really drives home how important the work that we do is to keep species from winking out forever."

Researchers said the discovery offers a unique view into the past, while also providing an understanding of preservation and sustainability for the days ahead. 

"Fossils are our only opportunity to see into past biodiversity," Garcia explained, adding, "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."