10,000-year-old fossilized mastodon tooth discovered in Midpen preserve
Fossil discovered in a creek within the forests of San Mateo County
Los Altos, CA— An exceptionally preserved fossilized tooth belonging to an ancient Pacific mastodon (Mammut pacificus) was recently discovered in a Midpeninsula Regional Open Space District (Midpen) preserve in San Mateo County.
The fossil was discovered in a creek bed by Brigid Lynch, a geomorphologist with Balance Hydrologics, during field surveys for a Midpen habitat enhancement project supporting the threatened California red-legged frog. What initially appeared to be an oddly shaped rock was later confirmed by paleontologists to be an intact, adult Pacific mastodon molar.
“As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this,” said Lynch.
Wayne Thompson, paleontologist and owner of Pacific Paleontology, described the extraordinary discovery for the region. “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. I had chills and shivers up and down my spine,” Thompson noted. “It's another puzzle in the Ice Age saga that we can put into place.”
The Pacific mastodon is the newest species of mastodon to be recognized and is distinguished from the American mastodon (Mammut americanum) by its narrower teeth, thicker leg bones, and difference in tusks. Researchers believe Pacific mastodons’ range included the areas of what is now California, Oregon, the northern Rocky Mountain region of the western United States and parts of Mexico.
Rendering of a Pacific mastodon by Haley Grunloh for Midpen. Researchers believe mastodons would wrap their trunks around branches, stripping the foliage off the tree to feed.
These massive herbivores roamed local ecosystems during the Pleistocene epoch, spanning 2.5 million years ago until their extinction around 11,700 years ago. Unlike mammoths, which were also present in the region and fed on grasses, mastodons were considered browsers, using their massive trunks to strip leaves, soft shoots or fruits of high-growing, generally woody plants.
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. Mountain lions and bobcats may have stalked prey alongside extinct saber-toothed cats and dire wolves, adapting to smaller game as the large herbivores vanished. Tule elk, coyotes and American badgers likely roamed the valleys inhabited by mastodons and bison-sized Jefferson’s ground sloths.
Pacific mastodons’ range included the areas of what is now California alongside other extinct native species such as Jefferson’s ground sloths (Megalonyx jeffersonii), western camels (Camelops hesternus) and Columbian mammoths (Mammuthus columbi). They overlapped with species still around today such as gray foxes (Urocyon cinereoargenteus), Steller’s jays (cyanocitta stelleri) and spotted owls (Strix occidentalis). Artwork courtesy of Mason Schratter.
To support ongoing scientific research, Midpen donated the fossilized tooth to Stanford University’s Doerr School of Sustainability. Researchers plan to utilize carbon dating on the molar to determine its exact age. The team at Stanford will perform a 3D-scan and print a copy of this specimen for Midpen's to use for public outreach and education.
“Fossils are our only opportunity to see into past biodiversity,” explained Christine Garcia, Curator and Manager of the Geoscience Specimen Collection at Stanford. “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.”
For Midpen staff, discovering the ancient remains during a modern restoration effort emphasizes Midpen’s mission to protect and restore the natural environment and its wild inhabitants.
“This highlights for me that the presence of mastodons wasn't that long ago, in geologic time,” said Midpen biologist Matt Sharp Chaney. “That mastodon were out here in the same landscape that we’re in today really drives home how important the work that we do is to keep species from winking out forever.”
Midpen’s mission is to acquire and preserve a regional greenbelt of open space land in perpetuity, protect and restore the natural environment, and provide opportunities for ecologically sensitive public enjoyment and education. On the Coast, Midpen has an expanded mission: to acquire and preserve in perpetuity open space and agricultural land of regional significance, protect and restore the natural environment, preserve rural character, encourage viable agricultural use of land resources, and provide opportunities for ecologically sensitive public enjoyment and education.
