A Scientist Wading Through a California Creek Found a 10,000 Year Old Mastodon Tooth in Immaculate Condition

The pristine molar belongs to a mastodon species scientists recognized only in 2019.

She came looking for copper, but found gold.

Earlier this year, geomorphologist Brigid Lynch was wading through a wooded creek in California’s San Mateo County, surveying habitat for the threatened California red-legged frog, when an oddly shaped object caught her eye.

“I keep joking it wasn’t hard to find,” Lynch told the Associated Press. “It was just sitting there in the middle of the creek, halfway in, half out of the water.”

The object was a fossilized mastodon molar, about 23 centimeters (9 inches) long and so well preserved that both its crown and roots remain intact. More surprisingly, it belonged to Mammut pacificus, the Pacific mastodon—a species scientists did not formally recognize until 2019.

The find adds another specimen to a still-young chapter in North American paleontology. Earlier, paleontologists treated California’s Ice Age mastodons as members of the widespread American mastodon, Mammut americanum. Then researchers took a closer look.

California’s Own Mastodon

In a 2019 study describing Mammut pacificus, paleontologists compared mastodon fossils from across western North America and found a consistent set of differences.

Pacific mastodons had narrower molars, thicker femurs and six fused vertebrae in the sacrum rather than five. Unlike some American mastodons, they also apparently lacked small tusks in the lower jaw. The researchers concluded that all known Pleistocene mastodon remains from California fit the Pacific species rather than M. americanum.

That makes the creek tooth part of a species whose history scientists have only recently begun disentangling.

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“The tooth itself is in immaculate condition. 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 who examined the fossil, said in a statement from the Midpeninsula Regional Open Space District. “I had chills and shivers up and down my spine. It’s another puzzle [piece] in the Ice Age saga that we can put into place.”

Mastodons resembled elephants, but they were not mammoths. They tended to be shorter and stockier, and their teeth reveal a different lifestyle. While many mammoths grazed on grasses, mastodons carried molars with large cone-shaped cusps suited to crushing leaves, twigs, and other woody vegetation.

Pacific mastodons roamed California and other parts of western North America during the Pleistocene, sharing the landscape with Columbian mammoths, giant ground sloths, and now-extinct camels.

Found from Oblivion

Exactly when this particular animal lived remains unknown.

The fossil molar is believed to be at least 10,000 years old, but researchers at Stanford University’s Doerr School of Sustainability, where the tooth now resides, hope to determine its age more precisely. They also plan to make a 3D replica for public education.

Its preservation immediately impressed Stanford curator Chrissy Garcia.

“It’s in great condition,” Garcia told the Associated Press. “So we’ve got both the crown and the root of the fossil. You can even see root canal.”

Mastodon fossils themselves are not particularly rare. Ron Tykoski, curator of vertebrate paleontology at the Perot Museum of Nature and Science, told the AP that they “pop up with some degree of frequency, depending on where you live.” Chance discoveries in eroding creeks, riverbanks, and beaches often bring fossils back to the surface.

The coincidence here is harder to miss.

Lynch uncovered evidence of an animal that vanished near the end of the Ice Age while surveying habitat for the California red-legged frog, a threatened species that has disappeared from much of its former range.

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A project intended to help preserve one piece of California’s living wildlife had unexpectedly uncovered another from a world long gone.

And the tooth is no longer lost in oblivion.