American Mastodon

The American mastodon, Mammut americanum, is an extinct North American proboscidean that lived from about 3.7 million years ago until about 10,000 BC. It was the last surviving member of the mastodon family. It is known from fossils found ranging from present-day Alaska and New England in the north, to Florida, southern California, and as far south as Honduras and El Salvador. Its main habitat was cold spruce woodlands, and it is believed to have browsed in herds.

 

The tusks of the American mastodon sometimes exceeded five meters in length; they curved upwards, but less dramatically than those of the woolly mammoth. Young males had vestigial lower tusks that were lost in adulthood. However, it has been proven that female mastodons had lower pairs of tusks. The tusks were probably used to break branches and twigs, although some evidence suggests males may have used them in mating challenges; one tusk is often shorter than the other, suggesting that, like humans and modern elephants, mastodons may have had laterality. Examination of fossilized tusks revealed a series of regularly spaced shallow pits on the underside of the tusks. Microscopic examination showed damage to the dentin under the pits. It is theorized that the damage was caused when the males were fighting over mating rights. The curved shape of the tusks would have forced them downward with each blow, causing damage to the newly forming ivory at the base of the tusk. The regularity of the damage in the growth patterns of the tusks indicates that this was an annual occurrence, probably occurring during the spring and early summer.

 

American Museum of Natural History, New York City, NY.

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