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''Aceros'' is a genus of large south-east Asian hornbills (Bucerotidae family). This genus sometimes includes all species generally placed in the genus ''Rhyticeros''. Alternatively, ''Aceros'' has been considered monotypic, only including the rufous-necked hornbill, in which case all of the remaining are moved to the ''Rhyticeros''. Additionally, the white-crowned hornbill is sometimes placed in this genus, but most now place it in ''Berenicornis'' instead. Among the species generally included in ''Aceros'', the rufous-necked hornbill is unique in that it lacks a conspicuous casque, and its bill is mainly dull yellowish. In fact, the genus, which means "no horn/hornless," is named really for the rufous-necked hornbill. All other species generally placed in ''Aceros'' have a relatively high casque and brightly coloured bills. ==Species== As generally recognized, the following species belong in ''Aceros'': * Rufous-necked hornbill, ''Aceros nipalensis'' * Knobbed hornbill, ''Aceros cassidix'' * Wrinkled hornbill, ''Aceros corrugatus'' * Writhed hornbill, ''Aceros leucocephalus'' * Walden's hornbill, ''Aceros waldeni'' An undescribed extinct hornbill species from Lifou in the Loyalty Islands, living until at least some 30.000 years ago, was initially placed in this genus. But its biogeography places it with the species now in ''Rhyticeros'' (Steadman, 2006). 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「Aceros」の詳細全文を読む スポンサード リンク
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