Mastodon molar found in California creek during frog survey

A geomorphologist surveying creeks for the threatened California red-legged frog stumbled on a fossilised Pacific mastodon molar in a San Mateo County preserve. The 23-cm tooth, estimated at 10,000 years old, has been donated to Stanford University for carbon dating and 3D scanning.

Bottom line — The immaculate molar, one of the most complete found locally, will help researchers reconstruct Ice Age ecosystems in the Bay Area.

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• Brigid Lynch of Balance Hydrologics initially thought the object was 'an oddly shaped rock' while working on a habitat restoration project for Midpeninsula Regional Open Space District, per the district's press release.
• Paleontologist Wayne Thompson of Pacific Paleontology confirmed it was an upper left third molar from an adult Pacific mastodon, noting it showed minor wear and likely came from an animal in its early 40s, according to KTVU.
• The Pacific mastodon (Mammut pacificus) was only formally identified as a distinct species in 2019, reported IFLScience, and differed from the American mastodon in having narrower teeth and thicker leg bones.
• Mastodons were browsers that stripped leaves and fruit from trees, unlike mammoths which grazed on grasses, the Midpeninsula district explained.
• Stanford curator Christine Garcia said the tooth includes both crown and root, with visible root canals, and that such discoveries are rare in this part of the US, per the Jamaica Star's AP report.
• The exact location within the Santa Cruz Mountains redwood forests is being kept confidential to protect the site, CBS News reported.
• Thompson told CBS that the tooth's excellent condition suggests the skull is nearby, and that Ice Age fossils are increasingly surfacing on construction sites due to environmental protections.

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