A unique bird found in swamps and forests of the Amazon and Orinoco river basins. It is the only member of the genus Opisthocomus and its taxonomic position has been the subject of much debate and is still far from clear. It is a herbivore and has an unusual digestive system with an enlarged crop for fermenting vegetable matter similar to that of ruminant mammals. Local names: ava serere, shansho, guacharaca de agua, pava hedionda.