Fossils discovered at a construction site in Silicon Valley, California's high-technology business hub, are believed to be 20 million years old, the San Jose Mercury News reports.
Among the natural relics were teeth from a 10-metre-long shark, teeth of an extinct hippopotamus-like creature, nine whale skulls and clams and barnacles, the paper said on Monday.
The fossils were unearthed by construction crews building a 66m-high dam at the Calaveras Reservoir, near the Northern California home of many of the world's largest technology corporations, and thousands of small startups.
"We started finding fossils here before construction even started," paleontologist Jim Walker told the paper.
"It was exciting. We were finding scallops, and I said, 'I want to get a whale.' And we did."
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So far more than 500 fossils from the Miocene epoch have been found at the site since 2011, when the construction work began.
The site is closed to the public, but the fossils will end up in a San Francisco museum, the paper said, citing the San Francisco Public Utilities Commission, which is building the dam.
Crews will continue to work together with scientists for the next two to three years until the new dam is completed. The dam is to replace a 1925 containment structure and is designed to better withstand earthquakes.
