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.
Common ostrichThe common ostrich (Struthio camelus), or simply ostrich, is a species of flightless bird native to certain large areas of Africa. It is one of two extant species of ostriches, the only living members of the genus Struthio in the ratite order of birds. The other is the Somali ostrich (Struthio molybdophanes), which was recognized as a distinct species by BirdLife International in 2014 having been previously considered a distinctive subspecies of ostrich. The common ostrich belongs to the order Struthioniformes.
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.
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).
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.
AfricaAfrica is the world's second-largest and second-most populous continent, after Asia in both aspects. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surface area. With billion people as of , it accounts for about of the world's human population. Africa's population is the youngest amongst all the continents; the median age in 2012 was 19.7, when the worldwide median age was 30.4.
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.
Arabian ostrichThe Arabian ostrich (Struthio camelus syriacus), Syrian ostrich, or Middle Eastern ostrich is an extinct subspecies of the ostrich that lived on the Arabian Peninsula and in the Near East until the mid-20th century. The Arabian ostrich's range seems to have been continuous in prehistoric times, but with the drying-up of the Arabian Peninsula, it disappeared from the inhospitable areas of the Arabian Desert, such as the Rub' al Khali.
Kiwi (bird)Kiwi (ˈkiːwi: ) are flightless birds endemic to New Zealand of the order Apterygiformes. The five extant species fall into the family Apterygidae (ˌæptəˈrɪdʒədi:) and genus Apteryx (ˈæptərɪks). Approximately the size of a domestic chicken, kiwi are the smallest ratites (which also include ostriches, emus, rheas, cassowaries and the extinct elephant birds and moas). DNA sequence comparisons have yielded the conclusion that kiwi are much more closely related to the extinct Malagasy elephant birds than to the moa with which they shared New Zealand.
Uropygial glandThe uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at the base of the tail (between the fourth caudal vertebra and the pygostyle) and is greatly variable in both shape and size. In some species, the opening of the gland has a small tuft of feathers to provide a wick for the preen oil (see below).
