Microraptor (Greek, μικρός, mīkros: "small"; Latin, raptor: "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They date from the early Cretaceous Jiufotang Formation (Aptian stage), 125 to 120 million years ago. Three species have been named (M. zhaoianus, M. gui, and M. hanqingi), though further study has suggested that all of them represent variation in a single species, which is properly called M.
A keel or carina (plural carinae) in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight. Not all birds have keels; in particular, some flightless birds lack a keel structure. Some flightless birds have a keel, such as the penguin; but in the penguin's case, its wings are too small for its body, so flight would require flapping its wings too fast to be practical.
The hoatzin (hoʊˈætsɪn ) or hoactzin (hoʊˈæktsɪn ) (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 is the only extant species in the genus Opisthocomus which is the only extant genus in the Opisthocomidae family under the order of Opisthocomiformes. The taxonomic position of this family has been greatly debated by specialists, and is still far from clear. It is notable for having chicks that have claws on two of their wing digits.
A number of animals are capable of aerial locomotion, either by powered flight or by gliding. This trait has appeared by evolution many times, without any single common ancestor. Flight has evolved at least four times in separate animals: insects, pterosaurs, birds, and bats. Gliding has evolved on many more occasions. Usually the development is to aid canopy animals in getting from tree to tree, although there are other possibilities.
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the elaborately woven hanging nest of the Montezuma oropendola or the village weaver—that is too restrictive a definition.
Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i.e. air flight or aviation) or through the vacuum of outer space (i.e. spaceflight). This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement. Many things can fly, from animal aviators such as birds, bats and insects, to natural gliders/parachuters such as patagial animals, anemochorous seeds and ballistospores, to human inventions like aircraft (airplanes, helicopters, airships, balloons, etc.
The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over eighty species of Enantiornithes have been named, but some names represent only single bones, so it is likely that not all are valid.
Bird 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.
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift.
Flight 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.
