Opisthocomidae is a family of

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s, the only named family within the order Opisthocomiformes. The only living representative is the

hoatzin The hoatzin ( ) or hoactzin ( ), (''Opisthocomus hoazin''), is the only species in the order Opisthocomiformes. It is a species of tropical bird found in swamps, riparian forests, and mangroves of the Amazon and the Orinoco basins in South Ameri ...

(''Opisthocomus hoazin'') which lives in the

Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technology c ...

and the

Orinoco delta The Orinoco Delta is a vast river delta of the Orinoco River, located in eastern Venezuela. Location The Orinoco Delta is one of the eight natural regions of Venezuela. It covers the whole of Delta Amacuro State and a few square kilometers of M ...

in South America. Several fossil species have been identified, including one from Africa and one from Europe.

Phylogeny

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 Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are often ...

), recent studies have favored Opisthocomidae's placement within the

Neoaves Neoaves is a clade that consists of all modern birds (Neornithes or Aves) with the exception of Paleognathae (ratites and kin) and Galloanserae (ducks, chickens and kin). Almost 95% of the roughly 10,000 known species of extant birds belong to ...

Taxonomy

* Family Opisthocomidae Swainson 1837Mikko's Phylogeny Archiv

** Genus ?†'' Foro (bird), Foro'' Olson 1992 (mid-Eocene, USA) - cuculiform? *** Species †'' Foro panarium'' Olson 1992 ** Genus ?†'' Onychopteryx'' Cracraft 1971 (Early Eocene of Argentina) – falconid? A ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'' *** Species †'' Onychopteryx simpsoni'' Cracraft 1971 ** Genus †'' Protoazin'' Mayr & De Pietri 2014 (late Eocene of France) *** Species †'' Protoazin parisiensis'' Mayr & De Pietri 2014 ** Genus †''

Namibiavis ''Namibiavis'' is an extinct genus of early hoatzin from early Middle Miocene (about 16 mya) deposits of Namibia. It was collected from Arrisdrift, southern Namibia. It was first named by Cécile Mourer-Chauviré in 2003 and the type specie ...

'' Mourer-Chauviré 2003 (Middle Miocene of Namibia) *** Species †'' Namibiavis senutae'' Mourer-Chauviré 2003 ** Genus †''

Hoazinavis ''Hoazinavis'' is an extinct genus of early hoatzin from Late Oligocene and Early Miocene (about 24–22 mya) deposits of Brazil. It was collected in 2008 from the Tremembé Formation of São Paulo, Brazil. It was first named by Gerald Mayr, H ...

'' Alvarenga, Mayr & Mourer-Chauviré 2011 (Late Oligocene and Early Miocene of Brazil) *** Species †'' Hoazinavis lacustris'' Alvarenga, Mayr & Mourer-Chauviré 2011 ** Genus †''

Hoazinoides ''Hoazinoides'' is an extinct genus of birds from the Miocene, Middle Miocene (Laventan) from the "Monkey Beds" of the Villavieja Formation of the Honda Group, Colombia, Honda Group at the Lagerstätte, Konzentrat-Lagerstätte of La Venta (Colom ...

'' Miller 1953 (middle Miocene of Colombia) *** Species †'' Hoazinoides magdalenae'' Miller 1953 ** Genus '' Opisthocomus'' Illiger 1811 *** Species ''

Opisthocomus hoazin The hoatzin ( ) or hoactzin ( ), (''Opisthocomus hoazin''), is the only species in the order Opisthocomiformes. It is a species of tropical bird found in swamps, riparian forests, and mangroves of the Amazon and the Orinoco basins in South Ameri ...

'' (Müller 1776) Illiger 1811 'Phasianus hoazin'' Müller 1776

Description

The only living representative is the

(''Opisthocomus hoazin''), which lives in the

and the

in South America. Several fossil species have been identified, including one from Africa and one from Europe. The

is a stunning, colourful bird from South America. The hoatzin is found in the rainforest of the Amazon. It has a long, permanently erected crest which gives the species a stunning 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. The nest is a flat platform in bush or tree above water. The chicks are

semi-precocial In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...

and leave the nest at about two to three weeks of age. The adults feed them with semi-digested slimy mass from their crops, and the young are fed during the first four or five months of their life. The young nestlings can jump out into the water, and swim with wings and feet, in order to escape predators at nest. Hoatzin embryos are known to develop very quickly compared to other birds. The

lives in tropical forested wetlands of 200 to 500 meters elevation. The hoatzin is an

arboreal Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...

species and is folivorous, feeding on leaves, flowers and fruits of a small number of plant species. It has a large crop that uses bacteria to break down the leaves that it eats. The hoatzin is unique because it has bacteria in its crop that breaks down its food while it is still in the crop. This is a process called

foregut fermentation Foregut fermentation is a form of digestion that occurs in the foregut of some animals. It has evolved independently in several groups of mammals, and also in the hoatzin bird. Foregut fermentation is employed by ruminants and pseudoruminants, so ...

. It rarely drinks because its diet includes 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

, the

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.

References

{{Taxonbar, from=Q942816 Higher-level bird taxa restricted to the Neotropics Monotypic bird families Opisthocomiformes Herbivorous vertebrates Extant Eocene first appearances