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The Amazon river dolphin (''Inia geoffrensis''), also known as the Boto or pink river dolphin, is a species of toothed whale classified in the family Iniidae. Three subspecies are currently recognized: ''I. g. geoffrensis'' (Araguaian river dolphin), ''I. g. boliviensis'' (Bolivian river dolphin) and ''I. g. humboldtiana'' (Orinoco river dolphin), which are distributed in the Amazon basin, the upper Madeira River in Bolivia, and the Orinoco basin, respectively. The Amazon river dolphin is the largest species of river dolphin, with adult males reaching in weight, and in length . Adults acquire a pink color, more prominent in males, giving it its nickname "pink river dolphin". Sexual dimorphism is very evident, with males measuring 16% and weighing 55% more than females. Like other toothed whales, they have a melon, and organ that is used for biosonar. The dorsal fin short in height, but nonetheless long, and their pectoral fins are also large. This feature, along with its medium size and the unfused cervical vertebrae, gives it great maneuverability to navigate the flooded forests and capture their prey. They has one of the widest diets among toothed whales; they feed mainly on fish, as many as 53 different species, such as croakers, catfish, tetras and piranhas, while also consuming other animals such as river turtles and freshwater crabs.〔 In 2008, it was ranked by the International Union for Conservation of Nature (IUCN) as a Data Deficient , due to the uncertainty regarding their population trends and the impact of threats. There has been significant hunting, but in recent decades, habitat loss and bycatch in fishing gear have become major threats. For its striking pink tinge, it is the only species of river dolphin kept in captivity, mainly in the United States, Venezuela and Europe ; however, it is difficult to train and a high mortality is seen in captive species. ==Taxonomy== The species ''Inia geoffrensis'' was described by Henri Marie Ducrotay de Blainville in 1817. The Amazon river dolphin belonged to the superfamily Platanistoidea (river dolphins), which used to constitute all river dolphins, which made them paraphyletic. Today, however, the Amazon river dolphin has been reclassified into the superfamily Inioidea.〔 There is no consensus on when and how they penetrated the Amazon basin; they may have done during the Miocene from the Pacific Ocean, before the formation of the Andes, or from the Atlantic Ocean.〔 Three subspecies are recognized:〔 ''I. g. geoffrensis'' (Araguaian river dolphin), ''I. g. boliviensis'' (Bolivian river dolphin) and ''I. g. humboldtiana'' (Orinoco river dolphin).〔 However, based on skull morphology in 1994, it was proposed that ''I. g. boliviensis'' was a different species.〔 In 2002, following the analysis of mitochondrial DNA specimens from the Orinoco basin, the Putumayo River (tributary of the Amazon) and the Tijamuchy and Ipurupuru rivers , in the Bolivian Amazon, a study concluded that genus ''Inia'' was divided into at least two evolutionary lineages: one restricted to the river basins of Bolivia and the other widely distributed in the Orinoco and Amazon; until 2009, the matter remained unresolved. 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「Amazon river dolphin」の詳細全文を読む スポンサード リンク
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