51-511: Confuciusornithidae is an extinct family of pygostylian avialans known from the Early Cretaceous , found in northern China . They are commonly placed as a sister group to Ornithothoraces , a group that contains all extant birds along with their closest extinct relatives. Confuciusornithidae contains four genera, possessing both shafted and non-shafted (downy) feathers. Some specimens probably referable to this clade represents one of
102-439: A Late Cretaceous origin (around 70 million years ago), but found that this early divergence is shared with a majority of extant bird orders, making it no more primitive than them. With respect to other material evidence, an undisputed fossil record of a close hoatzin relative is specimen UCMP 42823, a single cranium backside. It is of Miocene origin and was recovered in the upper Magdalena River Valley , Colombia , in
153-478: A digestive system capable of fermentation and the effective breaking-down of plant matter, a trait more commonly known from herbivorous ungulate - ruminant mammals and some primates . This bird is also the national bird of Guyana, where the local name for this bird is Canje pheasant . The hoatzin is pheasant -sized, with a total length of 65 cm (26 in), and a long neck and small head. It has an unfeathered blue face with maroon eyes, and its head
204-442: A rumen (a specialized, chambered stomach for bacterial fermentation), the hoatzin has an unusually large crop that is folded into two chambers, with a large, multi-chambered lower esophagus. Serrations on the beak help cut leaves into smaller pieces before they are swallowed. Because they lack the teeth of mammals, hoatzins don't regurgitate their food, or chew the cud ; instead, a combination of muscular pressure and abrasion by
255-588: A consonant) "behind" and κόμη kómē "hair" altogether meaning "long hair behind" referring to its large crest . The hoatzin was originally described in 1776 by German zoologist Statius Müller . Much debate has occurred about the hoatzin's relationships with other birds. Because of its distinctness, it has been given its own family , the Opisthocomidae, and its own suborder , the Opisthocomi. At various times, it has been allied with such taxa as
306-516: A node-based clade , "the common ancestor of the Confuciusornithidae and Neornithes plus all its descendants". In 2001, Jacques Gauthier and Kevin de Queiroz recommended that Chatterjee's original apomorphy-based clade concept be used instead of Chiappe's node-based definition, but this recommendation has been inconsistently followed. Luis Chiappe and co-authors continue to use Chiappe's definition, often attributing authorship of
357-427: A “cornified” lining of the crop is used as an equivalent to remastication , allowing fermentation and trituration to occur at the same site. The fermented foliage produces methane which the bird expels through burping. Its stomach chamber and gizzard are much smaller than in other birds. Its crop is so large as to displace the flight muscles and keel of the sternum, much to the detriment of its flight capacity. The crop
408-422: Is Protoazin parisiensis , from the latest Eocene (about 34 Mya) of Romainville , France . The holotype and only known specimen is NMB PG.70, consisting of partial coracoid , partial scapula , and partial pedal phalanx . According to the phylogenetic analysis performed by the authors, Namibiavis , although later, is more basal than Protoazin . Opisthocomiforms seem to have been much more widespread in
459-472: Is a group of avialans which includes the Confuciusornithidae and all of the more advanced species, the Ornithothoraces . The group Pygostylia was intended to encompass all avialans with a short, stubby tail, as opposed to the longer, unfused tails of more primitive species like Archaeopteryx lithographica . It was named by Sankar Chatterjee in 1997. Luis Chiappe later defined Pygostylia as
510-456: Is another extinct genus of early opisthocomiforms from early Middle Miocene (around 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 species is Namibiavis senutae . The hoatzin is a folivore —it eats the leaves (and to a lesser degree, the fruits and flowers ) of the plants that grow in its marshy and riverine habitat. It clambers around along
561-421: Is mainly visible when the hoatzin opens its wings. It is a noisy bird, and makes a variety of hoarse calls , including groans, croaks, hisses, and grunts. These calls are often associated with body movements, such as wing spreading. Hoatzin chicks have two claws on each wing. Immediately after hatching, they can use these claws, and their oversized feet, to scramble around the tree branches without falling into
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#1732790951250612-471: Is purely opportunistic or accidental. One of this species' many peculiarities is its unique digestive system, which contains specialized bacteria in the front part of the gut that break-down and ferment the foliar material they consume (much like cattle and other ruminants do). This process is more efficient than what has been measured in many other species of birds, with up to 70% of the plant fiber being digested. Unlike ruminants, however, which possess
663-407: Is seen in the nestlings of the hoatzin , an extant South American bird. The biomechanics of the wing itself are quite contentious due to a combination of traits that imply different modes of flight. Confuciusornithids possessed long primary feathers similar to those of modern fast-flapping birds, as opposed to gliding birds which have short primaries relative to their size. However, the narrowness of
714-455: Is supported by a thickened skin callus on the tip of the sternum, which helps the bird support the crop on a branch during rest and while digesting its food. A hoatzin's meal takes up to 45 hours to pass through its body. With a body weight as low as 700 grams (1.5 lb), the adult hoatzin is the smallest known animal with foregut fermentation (the lower limit for mammals is about 3 kilograms or 6.6 pounds). Because of aromatic compounds in
765-485: Is the only extant species in the genus Opisthocomus which is the only extant genus in the Opisthocomidae family under the order of Opisthocomiformes . Despite being the subject of intense debate by specialists, the taxonomic position of this family is still far from clear. The hoatzin is notable for its chicks having primitive claws on two of their wing digits ; the species also is unique in possessing
816-535: Is the presence of a toothless jaw, which shows a more birdlike adaptation compared to Archaeopteryx . The other defining features are as follows, according to Chiappe et al. (1999): Confuciusornithidae is the most basal group of the clade Pygostylia , whose members possess a pygostyle , a fused set of caudal vertebrae at the end of the tail. The pygostyle replaced the longer, unfused tail found in more primitive avialans such as Archaeopteryx , and may have served to improve flight. Pygostylia includes all modern birds,
867-425: Is topped by a spiky, rufous crest. The long, sooty-brown tail is bronze-green tipped with a broad whitish or buff band at the end. The upper parts are dark, sooty brown-edged buff on the wing coverts , and streaked buff on the mantle and nape. The underparts are buff, while the crissum (the undertail coverts surrounding the cloaca ), primaries , underwing coverts, and flanks are rich rufous- chestnut , but this
918-701: Is uncertain. [REDACTED] [REDACTED] Hoatzin Phasianus hoazin Müller, 1776 The hoatzin ( / h oʊ ˈ æ t s ɪ n / hoh- AT -sin ) or hoactzin ( / h oʊ ˈ æ k t s ɪ n / hoh- AKT -sin ) ( Opisthocomus hoazin ) is a species of tropical bird found in swamps, riparian forests, and mangroves of the Amazon and the Orinoco basins in South America . It
969-425: Is well suited for skimming prey off of the top of a body of water. Large numbers of fossils appear to originate from the tops of freshwater lakes, further supporting the water feeding connection. The remains of fish have been found in fossils of C. sanctus . Confuciusornithids appear to have been unable to take off from water and lacked the adaptations necessary to live aquatically. Thus, it appears that they flew along
1020-574: The Phaethoquornithes (containing numerous aquatic bird orders). The combined group was found to be sister to the Mirandornithes ( flamingos and grebes ). In 2015, genetic research indicated that the hoatzin is the last surviving member of a bird line that branched off in its own direction 64 million years ago, shortly after the extinction event that killed the nonavian dinosaurs. Another genetic study from 2024 instead suggested
1071-743: The Turgai Sea closed, marking the boundary between the Eocene and the Oligocene . None of these predators, and for the matter, no placental predator at all was present in South America before the Great American Interchange 3 Mya; this absence could explain the survival of the hoatzin there. In addition to being the earliest fossil record of an opisthocomiform, Protoazin was also the earliest find of one (1912), but it
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#17327909512501122-437: The cladogram below: † Archaeopteryx † Jeholornis † Sapeornis Jinguofortis Cratonavis Chongmingia † Confuciusornithidae Ornithuromorpha † Enantiornithes Pygostylia has been recovered as being within the clade Avebrevicauda . Avebrevicauda (meaning "birds with short tails") is a group of birds which includes all avialan species with ten or fewer free vertebrae in
1173-456: The rainy season , the exact timing of which varies across their range. Hoatzins are gregarious and nest in small colonies , laying two or three eggs in a stick nest in a tree hanging over water in seasonally flooded forests. The chicks are fed on regurgitated fermented food. In Brazil, indigenous peoples sometimes collect the eggs for food, and the adults are occasionally hunted, but it is generally rare to consume mature birds, as hoatzin meat
1224-469: The tinamous , the Galliformes (gamebirds), the rails , the bustards , seriemas , sandgrouse , doves , turacos and other Cuculiformes , and mousebirds . A whole genome sequencing study published in 2014 places the hoatzin as the sister taxon of a clade composed of Gruiformes (cranes) and Charadriiformes (plovers). Another genomic study in 2024 instead places it as the sister group to
1275-650: The Late Eocene and the Early Miocene in Europe, and of Namibiavis after the Middle Miocene of sub-Saharan Africa is the arrival of arboreal carnivorans —predation which could have had a devastating effect on the local opisthocomiforms, if they were similarly poor flyers and had a similarly vulnerable nesting strategies as today's hoatzins. Felids and viverrids first arrived in Europe from Asia after
1326-538: The Pygostylia share four unique characteristics . The trait that gives the group its name is the presence of a pygostyle , or set of fused vertebrae at the end of the tail. Next is the absence of a hyposphene - hypantrum . Next is a reversed pubic bone separated from the main axis of the sacrum by an angle of 45 to 65 degrees. Last is a bulbous medial condyle of the tibiotarsus (lower leg bone). The pygostylians fall into two distinct groups with regard to
1377-521: The branches in its search for food. The hoatzin uses a leathery “bump” on the bottom of its crop to help balance its weight on the branches. The species was once thought to eat the leaves of only arums and mangroves , but the species is now known to consume the leaves of more than 50 botanical species. One study, undertaken in Venezuela , found that the hoatzin's diet was 82% leaves, 10% flowers, and 8% fruit. Any feeding on insects or other animal matter
1428-419: The earliest known fossil evidence of primary feather moulting . They are also noted for their distinctive pair of ribbon-like tail feathers of disputed function. The wing anatomy of confuciusornithids suggests an unusual flight behavior, due to anatomy that implies conflicting abilities. They possessed feathers similar to those of fast-flapping birds, which rely on quick flapping of their wings to stay aloft. At
1479-409: The elimination of two thoracic vertebrae. The development of a pygostyle also shows better adaptation for flight, as this replaces the long tails present in earlier avialans. Similarly to Archaeopteryx , confuciusornithids possessed a large first digit with a hook-like claw. The digit implies a climbing lifestyle, as it serves to allow for hooking onto the grooves of trees. A similar anatomy and function
1530-497: The fossil bird Archaeopteryx , but the characteristic is rather an autapomorphy , possibly caused by an atavism toward the dinosaurian finger claws, whose developmental genetics ("blueprint") presumably is still in the avian genome . Since Archaeopteryx had three functional claws on each wing, some earlier systematists speculated that the hoatzin was descended from it, because nestling hoatzins have two functional claws on each wing. Modern researchers, however, hypothesize that
1581-531: The ground. The long feathers of the tail (central rectrices ) of confuciusornithids are of disputed function. Sexual dimorphism is an explanation, with males presumed to use the feathers in mating displays. However, it has been argued that the long rectrices were instead used as a defense against predators, as many birds shed feathers to protect themselves. The observation that less than 10% of confuciusornithid fossils possess these feathers supports this, as they may have been shed either in response to predators, or to
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1632-572: The leaves they consume, and the bacterial fermentation required to digest them, the birds have a disagreeable, manure -like odor and are only hunted by humans for food in times of dire need; local people also call it the "stinkbird" because of it. Much of the hoatzin’s diet, including various types of Monstera , Philodendron and other aroids , contains a high concentration of calcium oxalate crystals , which, even in small amounts, can be greatly uncomfortable (and even dangerous) for humans to consume. Hoatzins are seasonal breeders, breeding during
1683-483: The light of the supposed affiliation of the hoatzins and the Galliformes, which was the favored hypothesis at that time but had been controversial almost since its inception. He cautioned, however, "that Hoazinoides by no means establishes a phyletic junction point with other galliforms" for obvious reasons, as we know today. Anything other than the primary findings of Müller are not to be expected in any case, as by
1734-437: The name to Chiappe 2001 or Chiappe 2002 rather than to Chatterjee. Cladogram following the results of a phylogenetic study by Jingmai O'Connor and colleagues in 2016: † Confuciusornithiformes † Didactylornis † Sapeornis Ornithothoraces In 2023, Li et al recovered their new taxon, Cratonavis , as the new jinguofortisid that belongs to Pygostylia. The results of their phylogenetic analyses are shown in
1785-533: The only living members of the clade. Additional members have been added to Confuciusornitidae since 1999. Jinzhouornis was added by Hou, Zhou, and Zhang in 2002, and in 2008, Zhang, Zhou and Benton assigned the newly described genus Eoconfuciusornis to the family. Most confuciusornithids are known from the upper Jehol group , the Yixian Formation and Jiufotang Formation , dating from 125 to 120 million years ago. Eoconfuciusornis , however, predated
1836-577: The other confuciusornithids by 6 million years, dating to 131 Ma ago. The entire body of confuciusornithids was covered in contour feathers, except for the foot, base of beak, and the tarsometatarsus, the bone directly attached to the foot. It appears that they may also have had down feathers. The beaks of confuciusornithids show development of modern birdlike characteristics, such as a large beak and lack of teeth. The premaxilla and dentary are larger than those of Archaeopteryx . The anterior of these bones shows evidence of vasculature and innervation, implying
1887-472: The past, with the present South American distribution being only a relic. By the Early to Middle Miocene, they were probably extinct in Europe already, as formations dated to this time and representing fluvial or lacustrine palaeoenvironments, in which the hoatzin thrives today, have yielded dozens of bird specimens, but no opisthocomiforms. A possible explanation to account for the extinction of Protoazin between
1938-411: The presence of a beak. The lack of recovery of this structure indicates that the beak had a soft horny sheath. The softness of the beak along with the innervation suggest that the beak was sensitive, making it useful for searching for prey. Much of their anatomy resembles that of Archaeopteryx , especially the pectoral girdle and forelimbs. They were better adapted for flight than Archaeopteryx , due to
1989-616: The pygostyle. The Ornithothoraces have a ploughshare -shaped pygostyle, while the more primitive members had longer, rod-shaped pygostyles. The earliest known member of the group is the enantiornithine species Protopteryx fengningensis , from the Sichakou Member of the Huajiying Formation of China , which dates to around 131 Ma ago, though at least one other enantiornithine, Noguerornis , may be even older, at up to 145.5 million years ago, though its exact age
2040-469: The quite complete, but no less enigmatic Early-Middle Eocene ( Ypresian - Lutetian , some 48 Mya) Foro panarium are sometimes used to argue for a hoatzin-cuculiform (including turacos) link. As demonstrated above, though, this must be considered highly speculative, if not as badly off the mark as the relationship with the Cracidae discussed by Miller. The earliest record of the order Opisthocomiformes
2091-512: The same time, their wing anatomy also suggests a lack of flapping ability. Confuciusornithids are also noted for their beak and lack of teeth, similar to modern birds. Both predators and prey, confuciusornithid fossils have been observed with fish remains in their digestive systems and have themselves been found in the abdominal cavities of Sinocalliopteryx , a compsognathid predator. Archaeopteryx Jeholornis Sapeornis Confuciusornithidae Ornithothoraces Confuciusornithidae
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2142-443: The stress of the sudden death that produced the fossils. Confuciusornithids were first thought to be herbivorous due to the lack of teeth. However, their anatomy was not adapted for plant consumption, as gastroliths have never been found, nor did the weak rhamphotheca of the beak allow for grinding. Instead, the beak appears to have been sensitive enough to assist in food acquisition and capable of holding potential prey. This beak type
2193-807: The surface of the water, using their beak to search for fish. Confuciusornithid remains have been found in the abdominal contents of Sinocalliopteryx gigas , a compsognathid predator. Multiple confuciusornithids were present in the remains, implying that they were all captured in a short time. Confuciusornithids appear to have been social animals, as concurrently buried fossils are often found in close proximity. A 2018 study suggests that confuciusornithids could not have incubated their eggs like modern birds do. Other paravians (including Deinonychus ) and pterosaurs are known to be superprecocial and able to fly soon after birth, but for now there are no unambiguous confuciusornithid juveniles to attest this. [REDACTED] [REDACTED] Pygostylia Pygostylia
2244-533: The tail. The group was named in 2002 by Gregory S. Paul to distinguish short-tailed avialans from their ancestors, such as Archaeopteryx , which had long, reptilian tails. Depending on the analysis, Sapeornis may or may not be a member of Pygostylia, but is always within Avebrevicauda. Depending on the true phylogenetic position of Sapeornis , Avebrevicauda may be a junior synonym of Pygostylia. Chiappe noted that under his definition, all members of
2295-511: The time of Hoazinoides , essentially all modern bird families are either known or believed to have been present and distinct. Going further back in time, the Late Eocene or Early Oligocene (some 34 Mya) Filholornis from France has also been considered "proof" of a link between the hoatzin and the gamebirds. The fragmentary fossil Onychopteryx from the Eocene of Argentina and
2346-437: The water. When predators such as the great black hawk attack a hoatzin nesting colony, the adults fly noisily about, trying to divert the predator's attention, while the chicks move away from the nest and hide among the thickets. If discovered, however, they drop into the water and swim under the surface to escape, then later use their clawed wings to climb back to the safety of the nest. This has inevitably led to comparisons to
2397-468: The well-known fauna of La Venta . This has been placed into a distinct, less derived genus, Hoazinoides , but clearly would be placed into the same family as the extant species. It markedly differs in that the cranium of the living hoatzin is characteristic, being much domed, rounded, and shortened, and that these autapomorphies were less pronounced in the Miocene bird. Müller discussed these findings in
2448-400: The wings of confuciusornithids along with the lack of upstroke ability during flapping motion seem to preclude the ability to flap their wings quickly. Thus, they may have relied upon a flight method that no longer exists in modern birds. The hindlimbs of confuciusornithids did not resemble those of living birds. They were bad runners, with feet curved in a way that implies they did not move on
2499-448: The young hoatzin's claws are of more recent origin, and may be a secondary adaptation from its frequent need to leave the nest and climb about in dense vines and trees well before it can fly. A similar trait is seen in turacos , whose nestlings use claws on their wings to climb in trees. The generic name Opisthocomus comes from Ancient Greek ὄπισθοκομος ópisthokomos derived from ὄπισθε ópisthe ( ὄπισθεν ópisthen before
2550-425: Was first named by Hou et al. in 1995 to contain the type genus, Confuciusornis , and assigned to the monotypic clade Confuciusornithiformes within the class Aves . The group was given a phylogenetic definition by Chiappe, in 1999, who defined a node-based clade Confuciusornithidae to include only Changchengornis and Confuciusornis . There are a number of features that define the clade. The most significant
2601-509: Was forgotten for more than a century, being described only in 2014. Hoazinavis is an extinct genus of early opisthocomiforms 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 , Herculano Alvarenga and Cécile Mourer-Chauviré in 2011 and the type species is Hoazinavis lacustris . Namibiavis
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