The American mastodon, (†Mammut americanus) named by Kerr, 1792, is one of the best known and among the last species of †Mammut. Its earliest occurrences date from the early-middle Pliocene (early Blancan stage). It was formerly regarded (see below) as having a continent-wide distribution, especially during the Pleistocene epoch, known from fossil sites ranging from present-day Alaska, Ontario and New England in the north, to Florida, southern California, and as far south as Honduras.
In 1739, a French military expedition found the bones and teeth of an enormous creature along the Ohio River at Big Bone Lick in what would become the Commonwealth of Kentucky. These finds were forwarded to Buffon and other naturalists at the Jardin des Plantes (the precursor of today’s Muséum National d’Histoire Naturelle) in Paris.
The American mastodon has been widely thought to have resembled a woolly mammoth in appearance. However, consideration of the long tail (usually present in animals living in warm climates), size, body mass and environment implies the animal was not similarly hairy, and there is scant preserved evidence of body hair (what little has been recovered suggests a semiaquatic lifestyle). It had tusks that sometimes exceeded 5 m (16 ft) in length; they curved upwards, but less dramatically than those of the woolly mammoth. Its main habitat was cold spruce woodlands, and it is believed to have browsed in herds. It became extinct at the end of the Pleistocene approximately 11,000 years ago.