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Fossils in Southern California

The earliest fossils known in Southern California are found in the Kingston Range of the far northeastern Mojave Desert. The fossils represent microbial life forms and may date from Proterozoic times, as old as 1.5 billion years. During the Proterozoic, western North America was covered by ocean waters: fossils of ocean-dwelling organisms include trilobites (found in the Marble Mountains of San Bernardino County), ammonoids, corals, and other plant and invertebrate life forms.

During the Mesozoic Era- the Age of Dinosaurs-Southern California was an island arc with offshore volcanoes The earliest evidence of dinosaurs in California is in Early Jurassic dune sands along the eastern shore of an sea near today's Nevada border, where the only dinosaur tracks known in California are found. The remains of hadrosaurs ("duck-billed" dinosaurs) occur along the coast of California from San Francisco south to San Diego. A nodosaur, built like a tank and protected by thick armor, was found in San Diego. Fossils of plesiosaurs (huge swimming reptiles) have been found in Cajon Pass, north of San Bernardino.

From 65 million to 3 million years ago, Southern California was a vast, well-watered plain. Mammals flourished in tremendous variety: horses, 

camels, rhinoceros, giant bear-dogs, primitive elephants, early saber-toothed cats, and giraffe-like chalicotheres roamed the land. Notable occurrences of these fossils are found in the Barstow Fossil Beds and in Cajon Pass.

During the past 3 million years, the San Bernardino Mountains were uplifted along the San Andreas Fault. These mountains created a barrier that changed weather patterns, resulting in today's Mojave Desert. This period is colloquially called the "Ice Ages." Southern California in the Ice Ages had abundant animals such as saber-toothed cats, mastodons, mammoths, horses, giant camels, and ground sloths. Ice Age fossils are found throughout Southern California, including the "tar pits" at rancho La Brea and Diamond Valley Lake near Hemet.


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