Opisthocomidae

The phylogeny below is based on the work of Hughes & Baker 1999 and Mayr & De Pietri 2014. Traditionally classified among the fowl-like birds (Galliformes), recent studies have favored Opisthocomidae's placement within the Neoaves. }} ==Taxonomy==

• Family Opisthocomidae Swainson 1837 • Genus ?†Foro Olson 1992 (mid-Eocene, USA) - cuculiform? • Species †Foro panarium Olson 1992 • Genus ?†Onychopteryx Cracraft 1971 (Early Eocene of Argentina) – falconid? A nomen dubium • Species †Onychopteryx simpsoni Cracraft 1971 • Genus †Protoazin Mayr & De Pietri 2014 (late Eocene of France) • Species †Protoazin parisiensis Mayr & De Pietri 2014 • Genus †Namibiavis Mourer-Chauviré 2003 (Middle Miocene of Namibia) • Species †Namibiavis senutae Mourer-Chauviré 2003 • Genus †Hoazinavis Alvarenga, Mayr & Mourer-Chauviré 2011 (Late Oligocene and Early Miocene of Brazil) • Species †Hoazinavis lacustris Alvarenga, Mayr & Mourer-Chauviré 2011 • Genus †Hoazinoides Miller 1953 (middle Miocene of Colombia) • Species †Hoazinoides magdalenae Miller 1953 • Genus Opisthocomus Illiger 1811 • Species Opisthocomus hoazin (Müller 1776) Illiger 1811 [Phasianus hoazin Müller 1776] ==Description==

The only living representative is the hoatzin (Opisthocomus hoazin), which lives in the Amazon and the Orinoco delta in South America. The hoatzin is found in the rainforest of the Amazon. It has a long, permanently erected crest which gives the species a distinctive silhouette. This gregarious species is often found in groups of more than 40 birds, and up to 100 birds during breeding season which occurs during rainfalls. This is a process called foregut fermentation. It rarely drinks because its diet is high in water. The hoatzin is sedentary and widespread in suitable habitat. They are noisy birds, calling in unison, uttering large numbers of varied sounds. In addition to foregut fermentation, the hoatzin has a highly modified skeleton to accommodate its large crop, and in the young of this species, wing claws at the wrist joint which are used to climb among the branches of the nest tree. == Species by global population ==