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Dwarf elephants are prehistoric members of the order Proboscidea which, through the process of allopatric speciation on islands, evolved much smaller body sizes (around 1.5-2.3 metres) in comparison with their immediate ancestors. Dwarf elephants are an example of insular dwarfism, the phenomenon whereby large terrestrial vertebrates (usually mammals) that colonize islands evolve dwarf forms, a phenomenon attributed to adaptation to resource-poor environments and selection for early maturation and reproduction. Some modern populations of Asian elephants have also undergone size reduction on islands to a lesser degree, resulting in populations of pygmy elephants. Fossil remains of dwarf elephants have been found on the Mediterranean islands of Cyprus, Malta (at Ghar Dalam), Crete (in Chania at Vamos, Stylos and in a now under water cave on the coast), Sicily, Sardinia, the Cyclades Islands and the Dodecanese Islands. Other islands where dwarf stegodon have been found are Sulawesi, Flores, Timor, other islands of the Lesser Sundas and Central Java, all islands are in Indonesia. The Channel Islands of California once supported a dwarf species descended from Columbian mammoths, while small races of woolly mammoths were once found on Saint Paul Island; the mammoths on Wrangel island are no longer considered dwarfs. == Mediterranean Islands == Dwarf elephants first inhabited the Mediterranean islands during the Pleistocene, including all the major islands with the apparent exception of Corsica and the Balearics. Mediterranean dwarf elephants have generally been considered as members of the genus paleoloxodontine, derived from the continental straight-tusked elephant, ''Elephas (Palaeoloxodon) antiquus'' Falconer & Cautley, 1847. An exception is the dwarf Sardinian mammoth, ''Mammuthus lamarmorai'' (Major, 1883), the first endemic elephant of the Mediterranean islands recognized as belonging to the mammoth line. A genetic study published in 2006 theorized that the ''Elephas creticus'' could be from the mammoth line too. A scientific study of 2007 demonstrates the mistakes of the DNA research of 2006. During low sea levels, the Mediterranean islands were colonised again and again, giving rise, sometimes on the same island, to several species (or subspecies) of different body sizes. As the Ice Age came to an end, sea levels rose stranding elephants on the island. Low amounts of foliage for food lead to a shrinking of species (every 100,000 generations ()) resulting in dwarf elephants as fossil remains have proved. The island of Sicily appears to have been colonised by proboscideans in at least three separate waves of colonisation. These endemic dwarf elephants were taxonomically different on each island or group of very close islands, like the Cyclades archipelago. There are many uncertainties about the time of colonisation, the phylogenetic relationships and the taxonomic status of dwarf elephants on the Mediterranean islands. Extinction of the insular dwarf elephants has not been correlated with the arrival of humans to the islands. Furthermore, it has been suggested by the palaeontologist Othenio Abel in 1914,〔Abel's surmise is noted by Adrienne Mayor in ''The First Fossil Hunters: Paleontology in Greek and Roman Times'' (Princeton University Press) 2000. (illus. ed., 2001: ISBN 0691089779 ) 〕 that the finding of skeletons of such elephants sparked the idea that they belonged to giant cyclopses, because the center nasal opening was thought to be a cyclopic eye socket. 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「Dwarf elephants are prehistoric members of the order Proboscidea which, through the process of allopatric speciation on islands, evolved much smaller body sizes (around 1.5-2.3 metres) in comparison with their immediate ancestors. Dwarf elephants are an example of insular dwarfism, the phenomenon whereby large terrestrial vertebrates (usually mammals) that colonize islands evolve dwarf forms, a phenomenon attributed to adaptation to resource-poor environments and selection for early maturation and reproduction. Some modern populations of Asian elephants have also undergone size reduction on islands to a lesser degree, resulting in populations of pygmy elephants.Fossil remains of dwarf elephants have been found on the Mediterranean islands of Cyprus, Malta (at Ghar Dalam), Crete (in Chania at Vamos, Stylos and in a now under water cave on the coast), Sicily, Sardinia, the Cyclades Islands and the Dodecanese Islands. Other islands where dwarf stegodon have been found are Sulawesi, Flores, Timor, other islands of the Lesser Sundas and Central Java, all islands are in Indonesia. The Channel Islands of California once supported a dwarf species descended from Columbian mammoths, while small races of woolly mammoths were once found on Saint Paul Island; the mammoths on Wrangel island are no longer considered dwarfs.== Mediterranean Islands ==Dwarf elephants first inhabited the Mediterranean islands during the Pleistocene, including all the major islands with the apparent exception of Corsica and the Balearics. Mediterranean dwarf elephants have generally been considered as members of the genus paleoloxodontine, derived from the continental straight-tusked elephant, ''Elephas (Palaeoloxodon) antiquus'' Falconer & Cautley, 1847. An exception is the dwarf Sardinian mammoth, ''Mammuthus lamarmorai'' (Major, 1883), the first endemic elephant of the Mediterranean islands recognized as belonging to the mammoth line. A genetic study published in 2006 theorized that the ''Elephas creticus'' could be from the mammoth line too. A scientific study of 2007 demonstrates the mistakes of the DNA research of 2006.During low sea levels, the Mediterranean islands were colonised again and again, giving rise, sometimes on the same island, to several species (or subspecies) of different body sizes. As the Ice Age came to an end, sea levels rose stranding elephants on the island. Low amounts of foliage for food lead to a shrinking of species (every 100,000 generations ()) resulting in dwarf elephants as fossil remains have proved. The island of Sicily appears to have been colonised by proboscideans in at least three separate waves of colonisation. These endemic dwarf elephants were taxonomically different on each island or group of very close islands, like the Cyclades archipelago. There are many uncertainties about the time of colonisation, the phylogenetic relationships and the taxonomic status of dwarf elephants on the Mediterranean islands. Extinction of the insular dwarf elephants has not been correlated with the arrival of humans to the islands. Furthermore, it has been suggested by the palaeontologist Othenio Abel in 1914,Abel's surmise is noted by Adrienne Mayor in ''The First Fossil Hunters: Paleontology in Greek and Roman Times'' (Princeton University Press) 2000. (illus. ed., 2001: ISBN 0691089779 ) that the finding of skeletons of such elephants sparked the idea that they belonged to giant cyclopses, because the center nasal opening was thought to be a cyclopic eye socket.」の詳細全文を読む スポンサード リンク
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