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Giant Beaver

The Giant Beaver (Castoroides ohioensis) was a huge species of rodent, with a length up to 2.5 m (8.2 ft)^[1] and an estimated weight of 60-100 kg (130-220 lbs); past estimates went up to 220 kg (485 lbs).^[2] It lived in North America during the Pleistocene epoch, and went extinct at the end of the last Ice Age, 10,000 years ago.^[3] The extinction of the Giant Beaver may have been due to ecological restructuring at the end of the Pleistocene.^[4] The arrival of humans in the Americas could have been a factor, but there is no evidence that humans hunted the Giant Beaver.^[3] It was one of the abundant Pleistocene megafauna ? a wide variety of very large mammals that lived during the Pleistocene.

Fossils of the Giant Beaver are concentrated around the Midwestern United States in states near the Great Lakes, particularly Illinois and Indiana, but specimens are recorded from Alaska and Canada to Florida.^[1] Specimens from Florida have been placed in a subspecies, Castoroides ohioensis dilophidus, based on differences in premolar and molar features.^[5]

One of the important anatomical differences between the Giant Beaver and modern beaver species, besides size, is the structure of their teeth. Modern beavers have chisel-like incisor teeth for gnawing on wood. The teeth of the Giant Beaver are bigger and broader, and grew to about 15 centimeters (6 inches) long.^[3] In addition, the tail of the Giant Beaver must have been longer but narrower, and its hind legs shorter.^[1] Its great bulk might have restricted its movement on land (although large squat-legged hippopotamuses can move on land with little difficulty).

The first Giant Beaver fossils were discovered in 1837 in a peat bog in Ohio,^[3] hence its species epithet ohioensis. Nothing is known on whether or not the Giant Beaver built lodges like modern beavers. In Ohio, there have been claims of a possible Giant Beaver lodge four feet high and eight feet in diameter, formed from small saplings.^[3] The recent discovery of clear evidence for lodge building in the related genus Dipoides indicates that the Giant Beaver probably also built lodges.^[6]

Folklore

Both the native Mi'kmaq people of Canada and the native Pocumtuck people of the Connecticut River Valley of Massachusetts have related significant myths about giant beavers; see Glooscap and Pocumtuck Range for details.