A geomorphologist has discovered a significant Ice Age fossil—a well-preserved molar from an ancient Pacific mastodon—while surveying a preserve in San Mateo County, California. Brigid Lynch, with Balance Hydrologics, found the tooth in a creek bed during field work aimed at enhancing habitat for the threatened California red-legged frog.
Initially mistaking the object for an unusually shaped rock, Lynch documented it and later identified it as an upper left third molar from an adult Pacific mastodon, estimated to have lived in its early 40s. "As a geologist, I’ve gone out and seen stuff in the field, but definitely nothing as exciting as this," Lynch stated.
The Pacific mastodon, a species recently recognized as distinct from the American mastodon, is characterized by narrower teeth and thicker leg bones. Wayne Thompson, a paleontologist with Pacific Paleontology, described the molar as being in immaculate condition and the most complete and spectacular example he has seen from the region.
The discovered tooth has been donated to Stanford University’s Doerr School of Sustainability. Researchers plan to use carbon dating to establish the exact period the mastodon lived, its diet, and the local climate conditions of its time.
"I had chills and shivers up and down my spine, so 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," Thompson said. "It’s another puzzle in the Ice Age saga that we can put into place."
These large herbivores inhabited the region from approximately 2.5 million years ago until their extinction around 11,700 years ago. Unlike the grass-eating mammoths, mastodons were browsers that used their trunks to strip leaves, shoots, and fruit from woody plants.
"This find highlights for me that the presence of mastodons wasn’t that long ago, in geologic time," said Matt Sharp Chaney, a biologist with the Midpeninsula Regional Open Space District. "That mastodons were out here in the same landscape that I’m in today, 11,000 years ago roughly, really drives home how important the work we do is to keep species from winking out forever."
