Brigid Lynch was walking through a redwood forest in the San Mateo County hills when she noticed something unusual, half-submerged in the flowing water through a creek: a big smooth object that didn’t look like any of the other rocks.
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“It really stuck out,” she said. “I had no idea what it was. I thought maybe it was a mollusk or something, but that didn’t make sense since it wasn’t near the ocean.”
She took some photos, went home and entered them in Google photo search to solve the mystery. Lynch had made a remarkable discovery — she found a huge and surprisingly well-preserved molar from a Pacific mastodon, an extinct species of prehistoric elephant that roamed western North America during the Ice Age.
The 9-foot-tall creatures, which weighed up to 13,000 pounds, with long tusks and hair, were common in California and other Western states from more than 2.5 million years ago until about 11,000 years ago, along with saber-tooth tigers, camels, and other long-gone species. The tooth, a molar the size of a toaster, is one of the best preserved and most intact specimens ever found in the Bay Area, experts say.
“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,” said Wayne Thompson, a paleontologist and owner of Pacific Paleontology, a consulting firm based in Santa Cruz County. “I had chills and shivers up and down my spine. I was super happy to see this discovery because it can teach us a lot about the creatures themselves as a species and about this particular area. It’s another puzzle in the Ice Age saga that we can put into place.”
Lynch, a geomorphologist, made the discovery in March when the company she works for, Balance Hydrologics, based in Berkeley, was doing research as part of an effort to restore endangered red-legged frogs for the Midpeninsula Regional Open Space District.
The district isn’t saying exactly which of its preserves or what creek the molar was found in.
“We don’t really want people digging around in the creek looking for other fossils,” said Ryan McCauley, a district spokesman.
But he said it has inspired staff members at the agency, which owns a network of 26 preserves covering more than 70,000 acres in San Mateo and Santa Clara counties.
“My imagination goes to Jurassic Park with big ferns and dinosaurs,” McCauley said. “But this isn’t that. This is only about 10,000 years ago, when there were mammoths and saber-tooth tigers in the Bay Area. It isn’t that long ago. It boggles the mind.”
After Lynch realized she had discovered a mastodon molar, she asked colleagues who were out in the same forest if they could find it. They did. They put it in a bucket and brought it back. The company called experts at Stanford University, who also brought in Thompson. They confirmed it did indeed come from a mastodon, and today the fossil sits in Stanford University’s Doerr School of Sustainability’s collection.
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Researchers plan to use carbon dating and other techniques to determine its exact age, the mastodon’s diet and the local climate conditions when it lived.
“It’s pretty rare to just stumble across a fossil like this,” said Christine Garcia, specimen collection curator and manager for the Doerr School collection. “Most of these finds come from construction projects. For Brigid to have the eye to see this and know it is something special, that’s rare and unique.”
Every few years a major fossil discovery surfaces, she noted, such as in 2013 when workers rebuilding the dam at Calaveras Reservoir dug up a trove of prehistoric fossils, including teeth from huge megalodon sharks, whale skeletons, and hippo skeletons from 15 to 20 million years ago during the Miocene epoch, when the East Bay was covered by a shallow, tropical-like inland sea. Those fossils are now at UC Berkeley’s Museum of Paleontology.
Garcia said the mastodon tooth, which was sitting in the forest for thousands of years before the Roman Empire or before Egyptians built the pyramids, is not being displayed to the public. It’s currently in a temperature-controlled room at Stanford, where it is slowly drying out and being monitored, she said. Curators also have not put chemicals or other preservatives on it, which is common to preserve bones and fossils, for now, so it can be researched first.
“Because of how well-preserved it is, I don’t think it has been sitting in the creek the whole time,” Garcia said. “It probably washed out from somewhere more recently, like a hillside further upstream. When we get storms, there will be large slumps of land that can wash out at once. That’s often a time when fossils become exposed.”
Pacific mastodons are slightly different than mammoths. They had stockier body proportions and spent considerable time in forests, while mammoths were mostly grassland animals.
Although the Ice Age — 15,000 or 20,000 years ago — is a recent period in geologic time, it was a world very different from today’s. Because temperatures were cooler around the globe and much of the Earth’s water was locked up in ice, sea levels were roughly 300-400 feet lower than today. San Francisco Bay was a valley. And the edge of the Pacific Ocean was more than 20 miles farther west than it is now. Mastodons and other animals could walk out to the Farallon Islands, across a vast plain that is now hundreds of feet below the ocean’s surface.
People lived nearby and hunted mastodons, bison and other Ice Age animals.
“The Bay Area has been referred to as a Serengeti during the Ice Age, with plains and grasses and all kinds of animals roaming about, from mastodons to camels to saber-tooth tigers,” Garcia said. “Humans overlapped with these animals. They did not overlap with dinosaurs. This is a different, more recent time period. But particularly fascinating to think about what our area must have been like.”
Mastodons are believed to have eaten many of the same trees, like alders, that exist in the area today. Lynch said she sent photos of the huge tooth to lots of friends and family.
“I have never found anything like this before,” she said. “I’m terrible at finding cool rocks in the field. This was really unique. I was sharing it with everyone in my life. Everyone was so stoked. They texted their families. It really spread. It’s a once-in-a-lifetime thing.”
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