Mammoth construction of the Great Pyramid of ancient Egypt. The earliest known proboscideans, the clade that contains the elephants, existed about 55 million years ago around the Tethys Sea area. The closest relatives of the Proboscidea are the sirenians and the hyraxes. The family Elephantidae is known to have existed six million years ago in Africa, and includes the living elephants and the mammoths. Among many now extinct clades, the mastodon is only a distant relative of the mammoths, and part of the separate Mammutidae family, which diverged 25 million years before the mammoths evolved. The following cladogram shows the placement
Mastodon State Historic Site at the site in 1979 when scientists excavated a stone spear point made by hunters of the Clovis culture (14,000–10,000 years ago) in direct association with mastodon bones. This was the first solid evidence of the coexistence of people and these giant prehistoric beasts. The Kimmswick Bone Bed was added to the National Register of Historic Places in 1980. A museum tells the natural and cultural story of the oldest American Indian site one can visit in the state's park system. A full-size replica of a mastodon skeleton highlights the exhibits. A picnic area, hiking trails, and a special-use campground