MASTODON, a name given by Cuvier to those early f ore runners of the elephants (q.v.) which have nipple-like promi nences on the molar teeth. The generic term is now restricted by H. F. Osborn to a single species, Mastodon americanus, the American mastodon, but it is used familiarly to include a very large number of forms chiefly of Miocene and Pliocene age. For general account of these animals see the article PROBOSCIDEA.
The American mastodon is a large elephant which lived during Pleistocene times in the forests of eastern North America. It possesses molar teeth in which the ridges are placed transversely and are almost straight, the valleys between them not being blocked by intermediate cusps. The anterior molar possesses only three ridges. The upper tusks are large, devoid of enamel and upwardly directed, whilst the lower tusks are present only in the young animal as short, straight and forwardly directed spikes.
The ancestry of the American mastodon is unknown, but forms which are apparently closely allied have been discovered in China, whilst a series of European animals, culminating in Mastodon borsoni are usually regarded as related. This association is, how ever, denied by H. F. Osborn. Skeletons of the mastodon have been found in Ohio and in the Hudson valley; all over the United States, its remains have been recorded, but it is rare in the Middle West and South. It is usually found in the deposits laid down in a swamp or small pool, and it seems certain that the animal was a forest form, living upon trees. (See also ELEPHANT, MAMMOTH.) (D. M. S. W.) MASTOID: see EAR, ANATOMY OF; EAR, NOSE AND THROAT, DISEASES OF.