A routine infrastructure project in Oceanside, California, has uncovered a glimpse of a world that existed tens of millions of years before humans.
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that → uncover → humans
The City of Oceanside first announced the discovery on September 22, while reporting from the Los Angeles Times, NBC 7 San Diego and the San Diego Union-Tribune provided additional details about the excavation and the scientists working to identify the animal.
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reporting → announce → animal
The fossilised remains were found about 12 feet beneath the surface during excavation for a city water infrastructure project.
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remains → find → project
Several limb bones, ribs and other fragments were recovered, with the largest bone measuring more than two feet long, according to the Los Angeles Times.
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bone → recover → Times
What makes the discovery particularly intriguing is that scientists still cannot say exactly what animal the bones belonged to.
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bones → make → animal
A mystery buried beneath modern Oceanside
Paleontologist Joseph El Adli was conducting routine monitoring at the construction site when he spotted what appeared to be bone protruding from the excavation.
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what → bury → excavation
The discovery prompted the area to be secured and the excavation to shift from ordinary construction work to a careful fossil recovery operation.
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excavation → prompt → operation
The fossils were embedded in the Santiago Formation, a sequence of sedimentary rocks found across parts of northwestern San Diego County.
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fossils → embed → County
The particular section where the remains were found dates to the Eocene Epoch, a period that lasted from about 56 million to 33.9 million years ago.
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that → find → million
At the time, Southern California looked nothing like it does today.
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it → look → time
The region was warmer, wetter and heavily vegetated, providing habitat for large herbivorous mammals that have long since disappeared.
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that → vegetate → mammals
The fossils have been dated to roughly 40 to 45 million years ago, placing them within the Uintan North American Land Mammal Age.
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fossils → date → Age
Scientists have two possible suspects
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Scientists → have → suspects
Based on the size and shape of the recovered bones, El Adli has narrowed the possibilities to two extinct groups of odd-toed hoofed mammals.
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Adli → base → mammals
One is the Brontotheriidae, a family commonly associated with animals nicknamed thunder beasts.
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One → associate → animals
These large herbivores were related more distantly to today’s horses and rhinoceroses and included species with substantial bodies and distinctive skulls.
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herbivores → relate → bodies
Some brontotheres developed prominent bony projections on their noses.
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brontotheres → develop → noses
The other possibility is an amynodont, an extinct group of rhinoceros relatives sometimes described as swamp rhinos.
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possibility → describe → rhinos
They were generally hornless and had broad, barrel-shaped bodies.
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They → have → bodies
Some species are believed to have spent considerable time around water.
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species → believe → water
Both possibilities fit the broad picture provided by the bones, but the researchers need additional anatomical evidence before they can make a more precise identification.
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they → fit → identification
The skull, teeth or lower jaw would be particularly valuable because those features can provide clues that isolated limb bones cannot.
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bones → provide → clues
Seven days beneath tonnes of rock
Finding the fossils was only the beginning.
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Finding → find → fossils
Once the bones were spotted, El Adli and his team spent seven days carefully exposing them from several tonnes of hardened mudstone and sandstone.
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Adli → spot → mudstone
The work was done largely by hand to avoid damaging the fragile material.
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work → do → material
NBC 7 reported that roughly six feet of rock had to be removed by hand to reach the bones from the excavation where they were first identified.
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they → report → excavation
After the bones were exposed, they were protected inside a plaster field jacket.
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they → expose → jacket
This is a standard fossil-recovery technique that allows fragile specimens, along with some of the surrounding rock, to be transported without breaking apart.
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specimens → allow → rock
The fossils have now been moved to an off-site laboratory, where specialists will remove the remaining rock and stabilise the bones with conservation materials.
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specialists → move → materials
The find could reveal more about ancient California
The discovery is also significant because it adds to the growing fossil record of the Santiago Formation.
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it → reveal → Formation
Fossils from the formation have previously revealed that the San Diego region supported very different ecosystems during the Eocene.
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region → reveal → Eocene
Researchers hope that further preparation will reveal enough anatomical detail to identify the animal more precisely.
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preparation → hope → animal
If additional bones, teeth or jaw material are found at the site, they could provide even more information about the species and how it lived.
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it → find → species
For now, the City of Oceanside is keeping the precise discovery site confidential.
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City → keep → site
Officials say the decision is intended to protect both public safety around the active construction area and the fossil locality itself from unauthorised digging.
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decision → say → digging
The fossils are ultimately expected to become part of a museum collection, where they can be preserved and made available for scientific research and public viewing.
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they → expect → research
For a project designed to build part of modern Oceanside’s infrastructure, the excavation has unexpectedly opened a window into a much older California, one where enormous hoofed mammals moved through a warm, forested landscape roughly 40 million years ago.
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mammals → design → landscape
The Aporia
