This is an accepted version of this page
39-438: The nose is a protuberance in vertebrates which admits and expels air for respiration and contains olfactory receptors for sensing odors. Nose may also refer to: Nose A nose is a sensory organ and respiratory structure in vertebrates . It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils , or nares, a pair of tubes providing airflow through
78-470: A vomeronasal organ , lined by olfactory epithelium, but, unlike those of amniotes , this is generally a simple sac that, except in salamanders , has little connection with the rest of the nasal system. In reptiles , the nasal chamber is generally larger, with the choanae located much further back in the roof of the mouth. In crocodilians , the chamber is exceptionally long, helping the animal to breathe while partially submerged. The reptilian nasal chamber
117-473: 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
156-442: 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
195-456: A kind of filter against airborne illness. In addition to acting as a filter, mucus produced within the nose supplements the body's effort to maintain temperature, as well as contributes moisture to integral components of the respiratory system. Capillary structures of the nose warm and humidify air entering the body; later, this role in retaining moisture enables conditions for alveoli to properly exchange O 2 for CO 2 (i.e., respiration) within
234-418: A long, muscular, manipulative organ called the trunk . The vomeronasal organ of mammals is generally similar to that of reptiles. In most species, it is located in the floor of the nasal cavity, and opens into the mouth via two nasopalatine ducts running through the palate, but it opens directly into the nose in many rodents . It is, however, lost in bats, and in many primates, including humans. Fish have
273-400: A relatively good sense of smell. Unlike that of tetrapods , the nose has no connection with the mouth, nor any role in respiration. Instead, it generally consists of a pair of small pouches located behind the nostrils at the front or sides of the head. In many cases, each of the nostrils is divided into two by a fold of skin, allowing water to flow into the nose through one side and out through
312-416: A relatively poor sense of smell. The nasal cavity of mammals has been enlarged, in part, by the development of a palate cutting off the entire upper surface of the original oral cavity , which consequently becomes part of the nose, leaving the palate as the new roof of the mouth. The enlarged nasal cavity contains complex turbinates forming coiled scroll-like shapes that help to warm the air before it reaches
351-406: 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
390-717: 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)
429-533: Is called ornithology . Birds are feathered theropod dinosaurs and constitute 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
SECTION 10
#1732848467796468-408: Is divided into three parts: an anterior vestibule , the main olfactory chamber, and a posterior nasopharynx . The olfactory chamber is lined by olfactory epithelium on its upper surface and possesses a number of turbinates to increase the sensory area. The vomeronasal organ is well-developed in lizards and snakes, in which it no longer connects with the nasal cavity, opening directly into the roof of
507-429: 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
546-503: 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
585-516: 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,
624-530: 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
663-715: The Late Cretaceous and diversified dramatically around 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
702-660: 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
741-581: 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 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;
780-428: 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
819-509: 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
SECTION 20
#1732848467796858-665: 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
897-451: 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
936-439: The first interface between the external environment and an animal's delicate internal lungs, a nose conditions incoming air, both as a function of thermal regulation and filtration during respiration, as well as enabling the sensory perception of smell. Hair inside nostrils filter incoming air, as a first line of defense against dust particles, smoke, and other potential obstructions that would otherwise inhibit respiration, and as
975-416: The lungs. During exhalation, the capillaries then aid recovery of some moisture, mostly as a function of thermal regulation, again. The wet nose of dogs is useful for the perception of direction. The sensitive cold receptors in the skin detect the place where the nose is cooled the most and this is the direction a particular smell that the animal just picked up comes from. In amphibians and lungfish ,
1014-431: The lungs. The cavity also extends into neighbouring skull bones, forming additional air cavities known as paranasal sinuses . In cetaceans , the nose has been reduced to one or two blowholes , which are the nostrils that have migrated to the top of the head. This adaptation gave cetaceans a more streamlined body shape and the ability to breathe while mostly submerged. Conversely, the elephant 's nose has elaborated into
1053-473: The mouth. It is smaller in turtles, in which it retains its original nasal connection, and is absent in adult crocodilians. Birds have a similar nose to reptiles, with the nostrils located at the upper rear part of the beak . Since they generally have a poor sense of smell, the olfactory chamber is small, although it does contain three turbinates, which sometimes have a complex structure similar to that of mammals . In many birds, including doves and fowls ,
1092-438: The nasal passage was connected to the hypophysis . The same anatomy is observed in the most primitive living vertebrates, the lampreys and hagfish . In gnathostome ancestors, the olfactory apparatus gradually became paired (presumably to allow sense of direction of smells), and freeing the midline from the nasal passage allowed evolution of jaws. Bird Birds are a group of warm-blooded vertebrates constituting
1131-442: The nose for respiration . Where the nostrils pass through the nasal cavity they widen, are known as nasal fossae, and contain turbinates and olfactory mucosa . The nasal cavity also connects to the paranasal sinuses (dead-end air cavities for pressure buffering and humidification). From the nasal cavity, the nostrils continue into the pharynx , a switch track valve connecting the respiratory and digestive systems . In humans,
1170-419: The nose is located centrally on the face and serves as an alternative respiratory passage especially during suckling for infants . The protruding nose that is completely separate from the mouth part is a characteristic found only in therian mammals . It has been theorized that this unique mammalian nose evolved from the anterior part of the upper jaw of the reptilian-like ancestors ( synapsids ). Acting as
1209-470: The nostrils are covered by a horny protective shield. The vomeronasal organ of birds is either under-developed or altogether absent, depending on the species. The nasal cavities in mammals are both fused into one. Among most species, they are exceptionally large, typically occupying up to half the length of the skull. In some groups, however, including primates , bats , and cetaceans , the nose has been secondarily reduced, and these animals consequently have
Nose (disambiguation) - Misplaced Pages Continue
1248-446: The nostrils open into small sacs that, in turn, open into the forward roof of the mouth through the choanae . These sacs contain a small amount of olfactory epithelium, which, in the case of caecilians , also lines a number of neighbouring tentacles. Despite the general similarity in structure to those of amphibians, the nostrils of lungfish are not used in respiration, since these animals breathe through their mouths. Amphibians also have
1287-523: The only known groups without wings are the extinct moa and elephant birds . Wings, which are modified forelimbs , gave birds 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
1326-403: The other. The pouches are lined by olfactory epithelium, and commonly include a series of internal folds to increase the surface area, often forming an elaborate "olfactory rosette". In some teleosts , the pouches branch off into additional sinus-like cavities, while in coelacanths , they form a series of tubes. In the earliest vertebrates, there was only one nostril and olfactory pouch, and
1365-402: 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
1404-528: 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
1443-452: 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
1482-545: 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
1521-461: 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
#795204