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The pygmy mammoth or Channel Islands mammoth (''Mammuthus exilis'') is an extinct species of dwarf elephant descended from the Columbian mammoth (''M. columbi'') of mainland North America.〔Agenbroad 2010, p. 1.〕 This species went extinct during the Quaternary extinction event in which many megafauna species went extinct due to changing conditions to which the species could not adapt.〔Torben 2012, p. 3.〕 A case of island or insular dwarfism, from a recent analysis in 2010 it was determined that ''M. exilis'' was on average, tall at the shoulders and in weight, in stark contrast to its tall, ancestor. Another estimate gives a shoulder height of and a weight of . ==Discovery== Mammoth remains have been known on the northern Channel Islands of California since 1856. They were first reported in scientific literature in 1873. In July 1994, L. Agenbroad was called by the National Park Service to inspect an uncovered, unidentified skeleton found on the northeast coast of Santa Rosa Island. B. Agenbroad, L. Agenbroad, D. Morris, S. Morris, T. Rockwell and L. Roth 〔 found bones of the axial skeleton of a large land vertebrate on the Santa Rosa Island. On August 1994, they decided there was enough evidence to start to excavate and dig up the skeleton. They recovered 90% of a mature male Pygmy Mammoth's skeleton.〔 The mammoth was about 50 years old when it died.〔 The small bones were preserved in life position, which represented that it had died where it was found rather than being scattered around the island. The bones were returned to the Santa Barbara Museum of Natural History. After the discovery of the skeleton, a pedestrian survey of the island was started, which resulted in the discovery of 160 new locations of mammoth remains, the vast majority being found on Santa Rosa Island.〔 This was the first discovery of a nearly complete specimen of the pygmy mammoth. Fortunately enough, the skeleton of the mammoth was only missing a foot, a tusk, and a couple of vertebrae. The remains were covered by a sand dune, which prevented the bones from scattering and kept them intact. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pygmy mammoth」の詳細全文を読む スポンサード リンク
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