Anyone who’s ever found a tiny crinoid fossil in a meandering creek can attest to the wonder of finding something so old just lying around. Imagine the feeling you might have if you were to stumble upon a massive trove of fossilized animals and plants. This is what happened to one park ranger who accidentally discovered what might be the largest deposit of fossils ever found in California.

fossilized trunks found at Sierra Nevada foothills
Via: California State University, Chico

Greg Francek, a ranger and naturalist at the Mokelumne River Watershed which is managed by East Bay Municipal Utility District (EBMUD), came across a petrified tree in the protected area of the Sierra foothills in 2020, finding first one and then another and another until it became obvious that it was an entire ancient forest. The EBMUD has managed 28,000 acres of the land in the area for more than 100 years as melting snow run off from the mountains is a major supplier of water for Bay Area residents.

After weeks of searching the area a number of animal fossils were also found. Archaeologists were called in from the California State University, Chico to deal the huge quantity of fossils in the vicinity. Leading the academic study of the fossils are professors Russell Shapiro and Todd Greene, who have a team of students helping them to unearth and record every detail of the huge amount of fossils that were found in the watershed.

fossils from the Sierra Nevada foothills
Via: California State University, Chico

Among the fossilized finds are 2 mastodon skeletons with tusks, a dwarf or baby tapir, a rhino skeleton, and more than 600 petrified trees. The sheer number of fossils makes this an incredible site, but the variety of species present makes this an even rarer discovery. The last time mastodon fossils were found in California was in 1947.

The team has also found a fossilized giant tortoise and several tusks from gamphotheres- elephant-like creatures that were eventually replaced by mastodons in North and South America. The tusks date to the Miocene Epoch, a period of time dating to 23 million to 5.3 million years ago. One additional find of note are the bones of an aepycamelus, an ancient long-necked camelid that probably looked like a hybrid between a camel and a giraffe.

mastodon tooth fossils found in the Sierra Nevada foothills
Mastadon tooth fossils. Via: California State University, Chico

Some as-yet unknown species of ancient fish were also found at the site, along with many other birds and plant specimens from millions of years ago.

So far this huge area of densely scattered fossils is about 11 square miles, but researchers have found more fossils on each trip to the area. Since fossils could be anywhere on the site, they have to walk carefully and record any bones they find. For now the exact location has not been disclosed since the archaeological dig there is still ongoing.

archaeological dig at the Sierra Nevada foothills
Via: California State University, Chico