Flightless birdFlightless birds are birds that, through evolution, lost the ability to fly. There are over 60 extant species, including the well-known ratites (ostriches, emu, cassowaries, rheas, and kiwi) and penguins. The smallest flightless bird is the Inaccessible Island rail (length 12.5 cm, weight 34.7 g). The largest (both heaviest and tallest) flightless bird, which is also the largest living bird in general, is the ostrich (2.7 m, 156 kg).
PalaeognathaePalaeognathae (ˌpæliˈɒgnəθi; ) is a infraclass of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae contains five extant branches of flightless lineages (plus two extinct clades), termed ratites, and one flying lineage, the Neotropic tinamous.
Bird anatomyBird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations, mostly aiding flight. Birds have a light skeletal system and light but powerful musculature which, along with circulatory and respiratory systems capable of very high metabolic rates and oxygen supply, permit the bird to fly. The development of a beak has led to evolution of a specially adapted digestive system. Birds have many bones that are hollow (pneumatized) with criss-crossing struts or trusses for structural strength.
OstrichOstriches are large flightless birds. They are the heaviest living birds, and lay the largest eggs of any living land animal. With the ability to run at 70 km/h (43.5 mph), they are the fastest birds on land. They are farmed worldwide, with significant industries in the Philippines and in Namibia. Ostrich leather is a lucrative commodity, and the large feathers are used as plumes for the decoration of ceremonial headgear. Ostrich eggs have been used by humans for millennia.
TinamouTinamous ('tɪnəmuːz) form an order of birds called Tinamiformes (ˌtɪnəməˈfɔrmi:z), comprising a single family called Tinamidae (təˈnæmədi:), divided into two distinct subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" comes from the Galibi term for these birds, tinamu. Tinamous have traditionally been regarded as the sister group of the flightless ratites, but recent work places them well within the ratite radiation, implying basal ratites could fly.
CassowaryCassowaries (muruk, kasuari) are flightless birds of the genus Casuarius in the order Casuariiformes. They are classified as ratites: flightless birds without a keel on their sternum bones. Cassowaries are native to the tropical forests of New Guinea (Papua New Guinea and West Papua), the Aru Islands (Maluku), and northeastern Australia. Three cassowary species are extant. The most common, the southern cassowary, is the third-tallest and second-heaviest living bird, smaller only than the ostrich and emu.
EmuThe emu (ˈiːmjuː; Dromaius novaehollandiae) is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia, where it is the largest native bird and the only extant member of the genus Dromaius. The emu's range covers most of the mainland, but the Tasmanian, Kangaroo Island and King Island subspecies became extinct after the European settlement of Australia in 1788. Emus are soft-feathered, brown, flightless birds with long necks and legs, and can reach up to in height.
TheropodaTheropoda (θɪəˈrɒpədə; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma.
Flight featherFlight feathers (Pennae volatus) are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges ('rɛmᵻdʒiːz), singular remex ('riːmɛks), while those on the tail are called rectrices (rɛk'traɪsiːs), singular rectrix ('rɛktrɪks). The primary function of the flight feathers is to aid in the generation of both thrust and lift, thereby enabling flight.
FowlFowl are birds belonging to one of two biological orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl (Anseriformes). Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; together, they form the fowl clade which is scientifically known as Galloanserae (initially termed Galloanseri) (Latin gallus ("rooster") + ānser ("goose")). This clade is also supported by morphological and DNA sequence data as well as retrotransposon presence/absence data.
