A routine field survey in a California redwood forest has led to an extraordinary glimpse into the Ice Age.
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survey → lead → Age
A scientist searching a San Mateo County creek for signs of habitat conditions for threatened California red-legged frogs spotted an oddly shaped object that initially appeared to be an ordinary rock.
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that → search → object
Instead, it turned out to be a remarkably well-preserved tooth belonging to an extinct Pacific mastodon.
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it → turn → mastodon
The fossil is estimated to be at least 10,000 years old and is being described as an exceptionally complete specimen from the region.
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fossil → estimate → region
According to the Midpeninsula Regional Open Space District (Midpen), geomorphologist Brigid Lynch discovered the fossil while working on a habitat enhancement project for California red-legged frogs.
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Lynch → accord → frogs
Paleontologists later confirmed that the object was an intact molar from an adult Pacific mastodon, a giant herbivore that once roamed parts of western North America.
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that → confirm → America
From a strange-looking rock to an Ice Age fossil
Lynch, who works with Balance Hydrologics, was surveying a creek bed when she noticed the unusual object.
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she → look → object
Its shape was distinctive enough to catch her attention, but there was initially no indication that it had survived from a prehistoric animal.
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it → catch → animal
Paleontologists later examined the object and identified it as a molar from a Pacific mastodon.
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Paleontologists → examine → mastodon
The condition of the fossil made the discovery particularly significant.
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discovery → make → fossil
Wayne Thompson, a paleontologist and owner of Pacific Paleontology, described it as the most complete mastodon molar from the area and among the most impressive he had seen.
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he → describe → impressive
The exact location of the discovery has not been disclosed.
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location → disclose → discovery
Midpen officials said the information was being kept private partly to prevent people from attempting to search the area themselves for fossils.
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information → say → fossils
The fossil is estimated to be at least 10,000 years old (Image Credit: Midpeninsula Open Space District)
A giant herbivore from California's past
The fossil belonged to Mammut pacificus, commonly known as the Pacific mastodon.
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fossil → estimate → mastodon
Although mastodons are often associated with the better-known American mastodon, scientists recognise the Pacific mastodon as a distinct species.
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scientists → associate → species
The species was formally recognised in 2019 following research on mastodon remains from Southern California.
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species → recognise → California
Pacific mastodons differed from American mastodons in several physical characteristics, including narrower teeth, thicker leg bones and differences in their tusks.
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mastodons → differ → tusks
These animals were large herbivores that lived during the Pleistocene, an epoch that began roughly 2.5 million years ago and ended about 11,700 years ago.
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that → live → Pleistocene
They ranged across parts of western North America, with Pacific mastodon remains identified in California, Idaho, Oregon and, more recently, parts of Mexico.
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remains → range → Mexico
Unlike mammoths, which primarily grazed on grasses, mastodons were browsers that fed on leaves, shoots and other vegetation.
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that → graze → leaves
That makes the newly discovered tooth more than just an unusual fossil.
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tooth → make → fossil
It is a physical remnant of a landscape that existed thousands of years before modern California took shape.
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California → exist → shape
What the tooth could reveal
The fossil has now been donated to Stanford University's Doerr School of Sustainability for further study.
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fossil → reveal → study
Researchers plan to use carbon dating to determine its precise age rather than relying solely on the current estimate of at least 10,000 years.
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Researchers → plan → years
Scientists also intend to create a three-dimensional scan of the tooth.
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Scientists → intend → tooth
Midpen plans to use the resulting digital model and a replica for educational and public outreach purposes.
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Midpen → plan → purposes
According to the researchers, fossils such as this can help reconstruct past ecosystems and biodiversity.
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fossils → accord → ecosystems
By studying what lived in a region thousands of years ago, scientists can gain a better understanding of how landscapes and species have changed over time.
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landscapes → study → time
The discovery also creates an unexpected link between modern conservation and ancient history.
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discovery → create → conservation
Lynch was searching the landscape to support the habitat of a threatened frog species when she encountered evidence of an animal that disappeared thousands of years ago.
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that → search → years
For a moment, the creek bed offered a glimpse of a very different California, one where enormous mastodons moved through forests and other now-extinct animals shared the landscape.
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animals → offer → landscape
Today, that same environment is being studied and protected for species that are still here, making the accidental discovery a reminder of how dramatically ecosystems can change over time.
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ecosystems → study → time
The Aporia
