Writhed Hornbill (Aceros leucocephalus)
Aceros is a genus of of large south-east Asian hornbills in the 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.
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).
Knobbed Hornbill (Temminck, 1823) (Aceros cassidix) Wrinkled Hornbill (Temminck, 1832) (Aceros corrugatus) Writhed Hornbill (Vieillot, 1816) (Aceros leucocephalus) Rufous-necked Hornbill (Hodgson, 1829) (Aceros nipalensis) Walden's Hornbill (Sharpe, 1877) (Aceros waldeni)