Jefferson had long been fascinated with mastodons, a distant relative of the modern elephant. He was convinced the massive creatures still roamed the uncharted landscapes of North America and he told the explorers to keep a lookout for them. The expedition failed to sight any of the long-extinct mastodons, but they did describe 178 previously unknown species of plants and 122 new animals including coyotes, mountain beavers, prairie dogs, and grizzly bears. 

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