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44-537: The chachalacas, guans, and curassows are birds in the family Cracidae . These are species of tropical and subtropical Central and South America . The range of one species, the plain chachalaca , just reaches southernmost parts of Texas in the United States . Two species, the Trinidad piping guan and the rufous-vented chachalaca occur on the islands of Trinidad and Tobago respectively. The family Cracidae

88-474: A dinosaur . By comparison, speciation within curassows ( Crax , Nothocrax , Pauxi and Mitu ) and the piping/wattled guans is supported by better evidence. It was usually caused by changes in topography which divided populations ( vicariant speciation ), mainly due to the uplift of the Andes which led to the establishment of the modern river basins. The distribution of curassow and piping-guan species for

132-717: A better sense of smell. A third stage of bird evolution starting with Ornithothoraces (the "bird-chested" avialans) can be associated with the refining of aerodynamics and flight capabilities, and the loss or co-ossification of several skeletal features. Particularly significant are the development of an enlarged, keeled sternum and the alula , and the loss of grasping hands. † Anchiornis † Archaeopteryx † Xiaotingia † Rahonavis † Jeholornis † Jixiangornis † Balaur † Zhongjianornis † Sapeornis † Confuciusornithiformes † Protopteryx † Pengornis Ornithothoraces † Enantiornithes Morphology (biology) This includes aspects of

176-473: A definition similar to "all theropods closer to birds than to Deinonychus ", with Troodon being sometimes added as a second external specifier in case it is closer to birds than to Deinonychus . Avialae is also occasionally defined as an apomorphy-based clade (that is, one based on physical characteristics). Jacques Gauthier , who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight , and

220-509: A famous debate , which is said to exemplify the two major deviations in biological thinking at the time – whether animal structure was due to function or evolution. Most taxa differ morphologically from other taxa. Typically, closely related taxa differ much less than more distantly related ones, but there are exceptions to this. Cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire

264-442: A group called Paraves . Some basal members of Deinonychosauria, such as Microraptor , have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal , have been able to glide, or both. Unlike Archaeopteryx and the non-avialan feathered dinosaurs, who primarily ate meat, studies suggest that

308-525: A similar appearance as a result of convergent evolution or even mimicry . In addition, there can be morphological differences within a species, such as in Apoica flavissima where queens are significantly smaller than workers. A further problem with relying on morphological data is that what may appear morphologically to be two distinct species may in fact be shown by DNA analysis to be a single species. The significance of these differences can be examined through

352-406: A sister group, the order Crocodilia , contain the only living representatives of the reptile clade Archosauria . During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica . However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and

396-717: A time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (one male with many females) or, rarely, polyandrous (one female with many males). Birds produce offspring by laying eggs which are fertilised through sexual reproduction . They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs, meat, and feathers. Songbirds , parrots, and other species are popular as pets. Guano (bird excrement)

440-597: A very distinct and ancient lineage. In addition, the molecular data suggest that the Cracidae originated in the Late Cretaceous , but the authors caution that this cannot be more than a hypothesis at present: as the rate of molecular evolution is neither constant over time nor uniform between genera and even species, dating based on molecular information has a very low accuracy over such long timespans and needs to be corroborated by fossil evidence. The fossil record of cracids

484-429: Is harvested for use as a fertiliser. Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry. The first classification of birds

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528-649: Is known about the evolution and radiation of the Galloanserae , and consistent with the paleogeography of the Americas . The ichnotaxon Tristraguloolithus cracioides is based on fossil eggshell fragments from the Late Cretaceous Oldman Formation of southern Alberta, Canada which are similar to chachalaca eggs (Zelenitsky et al. , 1996), but in the absence of bone material their relationships cannot be determined except that they are apparently not from

572-419: Is limited to a single doubtfully distinct genus of chachalaca, Boreortalis (Hawthorn Early Miocene of Florida , USA; may actually be a junior synonym of Ortalis ) and some species in the modern genus Ortalis , however. This does not provide any assistance in evaluating the hypothesis (Pereira et al. , 2002) that the split between the 4 main lineages of our time occurred quite rapidly, approximately in

616-503: Is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor. Over 40% of key traits found in modern birds evolved during the 60 million year transition from the earliest bird-line archosaurs to the first maniraptoromorphs , i.e. the first dinosaurs closer to living birds than to Tyrannosaurus rex . The loss of osteoderms otherwise common in archosaurs and acquisition of primitive feathers might have occurred early during this phase. After

660-516: Is synonymous to Avifilopluma. † Scansoriopterygidae † Eosinopteryx † Jinfengopteryx † Aurornis † Dromaeosauridae † Troodontidae Avialae Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropod dinosaurs and, more specifically, members of Maniraptora , a group of theropods which includes dromaeosaurids and oviraptorosaurs , among others. As scientists have discovered more theropods closely related to birds,

704-530: Is used by many scientists including adherents to the PhyloCode . Gauthier defined Aves to include only the crown group of the set of modern birds. This was done by excluding most groups known only from fossils , and assigning them, instead, to the broader group Avialae, on the principle that a clade based on extant species should be limited to those extant species and their closest extinct relatives. Gauthier and de Queiroz identified four different definitions for

748-467: The Oligocene or slightly earlier, somewhere between 40 and 20 mya . The genera Procrax and Palaeonossax are often considered cracids, but this is not certain at all; they may belong to a related extinct lineage. Of these too, few good fossils are known, as they date to about the time when the modern groups presumably diverged. Should they be cracids, they are not unlikely to represent either some of

792-660: The Tiaojishan Formation of China, which has been dated to the late Jurassic period ( Oxfordian stage), about 160 million years ago. The avialan species from this time period include Anchiornis huxleyi , Xiaotingia zhengi , and Aurornis xui . The well-known probable early avialan, Archaeopteryx , dates from slightly later Jurassic rocks (about 155 million years old) from Germany . Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds but were later lost during bird evolution. These features include enlarged claws on

836-468: The little chachalaca ( Ortalis motmot ), at as little as 38 cm (15 in) and 350 g (12 oz), to the great curassow ( Crax rubra ), at nearly 1 m (39 in) and 4.3 kg (9.5 lb). These species feed on fruit, insects and worms. They build nests in trees, and lay two to three large white eggs , which only the female incubates alone. The young are precocial and are born with an instinct to immediately climb and seek refuge in

880-504: The only known living dinosaurs . Likewise, birds are considered reptiles in the modern cladistic sense of the term, and their closest living relatives are the crocodilians . Birds are descendants of the primitive avialans (whose members include Archaeopteryx ) which first appeared during the Late Jurassic . According to recent estimates, modern birds ( Neornithes ) evolved in the Late Cretaceous and diversified dramatically around

924-433: The 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) common ostrich . There are over 11,000 living species and they are split into 44 orders . More than half are passerine or "perching" birds. Birds have wings whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds . Wings, which are modified forelimbs , gave birds

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968-654: The Mikko's Phylogeny Archive and Paleofile.com websites. Alternatively, all subfamilies except the Penelopinae could be lumped into the Cracinae. As the initial radiation of cracids is not well resolved at present (see below), the system used here seems more appropriate. It is also quite probable that entirely extinct subfamilies exist as the fossil record is utterly incomplete. Recent research has analyzed mt and nDNA sequences , morphological , and biogeographical data to study

1012-480: The ability to fly, although further evolution has led to the loss of flight in some birds , including ratites , penguins , and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds , have further evolved for swimming. The study of birds is called ornithology . Birds are feathered theropod dinosaurs and constitute

1056-428: The appearance of Maniraptoromorpha, the next 40 million years marked a continuous reduction of body size and the accumulation of neotenic (juvenile-like) characteristics. Hypercarnivory became increasingly less common while braincases enlarged and forelimbs became longer. The integument evolved into complex, pennaceous feathers . The oldest known paravian (and probably the earliest avialan) fossils come from

1100-509: The birds that descended from them. Despite being currently one of the most widely used, the crown-group definition of Aves has been criticised by some researchers. Lee and Spencer (1997) argued that, contrary to what Gauthier defended, this definition would not increase the stability of the clade and the exact content of Aves will always be uncertain because any defined clade (either crown or not) will have few synapomorphies distinguishing it from its closest relatives. Their alternative definition

1144-665: The earliest members of Aves, is removed from this group, becoming a non-avian dinosaur instead. These proposals have been adopted by many researchers in the field of palaeontology and bird evolution , though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term "bird" by these researchers. † Coelurus † Ornitholestes † Ornithomimosauria † Alvarezsauridae † Oviraptorosauria   Paraves Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used

1188-451: The first avialans were omnivores . The Late Jurassic Archaeopteryx is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to display both clearly traditional reptilian characteristics—teeth, clawed fingers, and a long, lizard-like tail—as well as wings with flight feathers similar to those of modern birds. It

1232-452: The last members of the family before guans, chachalacas, etc. evolved, or very early representatives of these lineages. Thus, the assumption that the modern diversity started to evolve in the late Paleogene , continuing throughout the Miocene and onwards, must also be considered hypothetical given the lack of robust evidence. Still, the "molecular" scenario is entirely possible considering what

1276-408: The most part follows the layout of these river systems, and in the latter case, apparently many extinctions of populations in lowland areas (Grau et al. , 2005). Another result was that the wattled guan belongs to the same genus as the piping-guans, which thus use the older name Aburria (Grau et al. , 2005). Originally interpreted as a turkey by Othniel Charles Marsh , Meleagris antiquus

1320-423: The nesting tree. They are able to fly within days of hatching. Bird Birds are a group of warm-blooded vertebrates constituting the class Aves ( Latin: [ˈaveːs] ), characterised by feathers , toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart , and a strong yet lightweight skeleton . Birds live worldwide and range in size from

1364-402: The outermost half) can be seen in the evolution of maniraptoromorphs, and this process culminated in the appearance of the pygostyle , an ossification of fused tail vertebrae. In the late Cretaceous, about 100 million years ago, the ancestors of all modern birds evolved a more open pelvis, allowing them to lay larger eggs compared to body size. Around 95 million years ago, they evolved

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1408-465: The outward appearance (shape, structure, color, pattern, size), i.e. external morphology (or eidonomy ), as well as the form and structure of internal parts like bones and organs , i.e. internal morphology (or anatomy ). This is in contrast to physiology , which deals primarily with function. Morphology is a branch of life science dealing with the study of the gross structure of an organism or taxon and its component parts. The etymology of

1452-405: The phylogenetic relationships of cracid birds, namely the relationships among the genera (Pereira et al. , 2002), the relationships between the species of curassows (Pereira & Baker, 2004) and between the piping- and wattled guans (Grau et al. , 2005). The traditional groups—chachalacas, guans, and curassows—are verified as distinct clades , but the horned guan represents the sole survivor of

1496-528: The previously clear distinction between non-birds and birds has become blurred. By the 2000s, discoveries in the Liaoning Province of northeast China, which demonstrated many small theropod feathered dinosaurs , contributed to this ambiguity. The consensus view in contemporary palaeontology is that the flying theropods, or avialans , are the closest relatives of the deinonychosaurs , which include dromaeosaurids and troodontids . Together, these form

1540-452: The same biological name "Aves", which is a problem. The authors proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below. They assigned other names to the other groups.   Lizards & snakes   Turtles   Crocodiles   Birds Under the fourth definition Archaeopteryx , traditionally considered one of

1584-545: The second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial maneuvering. Avialans diversified into a wide variety of forms during the Cretaceous period. Many groups retained primitive characteristics , such as clawed wings and teeth, though the latter were lost independently in a number of avialan groups, including modern birds (Aves). Increasingly stiff tails (especially

1628-415: The smaller chachalacas are found in more open scrubby habitats. Many species are fairly long tailed, which may be an aide to navigating their largely arboreal existence. They are generally dull-plumaged, but the curassows and some guans have colourful facial ornaments. The birds in this family are particularly vocal, with the chachalacas taking their name from the sound of their call. Cracids range in size from

1672-852: The study by De Chen and collaborators published in 2021. The numbers of species are from the list maintained by Frank Gill , Pamela Rasmussen and David Donsker on behalf of the International Ornithologists' Union . Penelopina – highland guan [REDACTED] Chamaepetes – guans (2 species) Penelope – guans (16 species) [REDACTED] Aburria – wattled guan Pipile – piping guans (5 species) Oreophasis – horned guan [REDACTED] Ortalis – chachalacas (16 species) [REDACTED] Crax – curassows (7 species) [REDACTED] Pauxi – curassows (3 species) [REDACTED] Mitu – curassows (4 species) [REDACTED] Nothocrax – nocturnal curassow [REDACTED] Extinct species assignment follows

1716-600: The time of the Cretaceous–Paleogene extinction event 66 million years ago, which killed off the pterosaurs and all non- ornithuran dinosaurs. Many social species preserve knowledge across generations ( culture ). Birds are social, communicating with visual signals, calls, and songs , and participating in such behaviour as cooperative breeding and hunting, flocking , and mobbing of predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous , usually for one breeding season at

1760-576: The use of allometric engineering in which one or both species are manipulated to phenocopy the other species. A step relevant to the evaluation of morphology between traits/features within species, includes an assessment of the terms: homology and homoplasy . Homology between features indicates that those features have been derived from a common ancestor. Alternatively, homoplasy between features describes those that can resemble each other, but derive independently via parallel or convergent evolution . The invention and development of microscopy enabled

1804-763: The word "morphology" is from the Ancient Greek μορφή ( morphḗ ), meaning "form", and λόγος ( lógos ), meaning "word, study, research". While the concept of form in biology, opposed to function , dates back to Aristotle (see Aristotle's biology ), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Friedrich Burdach (1800). Among other important theorists of morphology are Lorenz Oken , Georges Cuvier , Étienne Geoffroy Saint-Hilaire , Richard Owen , Carl Gegenbaur and Ernst Haeckel . In 1830, Cuvier and Saint-Hilaire engaged in

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1848-461: Was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae . Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use. Birds are categorised as the biological class Aves in Linnaean taxonomy . Phylogenetic taxonomy places Aves in the clade Theropoda as an infraclass or a subclass, more recently a subclass. Aves and

1892-1101: Was introduced (as Craxia) by the French polymath Constantine Samuel Rafinesque in 1815. The Cracidae are an ancient group that were thought to be related to the Australasian mound-builders of family Megapodiidae . The two families they were sometimes united in a distinct order , Craciformes, as in Munroe and Sibley's 1993 World Checklist of Birds . However, the group is not monophyletic and more recent phylogenetic studies have found Megapodiidae and Cracidae to be successive early branching lineages of Galliformes . Megapodiidae – megapodes (7 genera, 21 extant species) [REDACTED] Cracidae – chachalacas, curassows, guans (11 genera, 57 species) [REDACTED] Numididae – guineafowl (4 genera, 8 species) [REDACTED] Odontophoridae – New World quail (10 genera, 34 species) [REDACTED] Phasianidae – pheasants & allies (54 genera, 188 species) [REDACTED] Cladogram based on

1936-471: Was referred to as Cracidae in 1964 by Pierce Brodkorb . It is nowadays considered unambiguously to be a Cariamiformes under Bathornithidae , and indeed a very different animal from cracids, being a 2 meter tall terrestrial predator. Similarly, Palaeophasianus has been reassigned to Geranoididae , a lineage of large, ostrich -like stem- cranes . Cracids are large birds, similar in general appearance to turkeys . The guans and curassows live in trees, but

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