aves

Century Dictionary and Cyclopedia

1. Birds; feathered animals, considered as a class of vertebrates,next after mammals: sometimes united with Reptilia in a superclass Sauropsida, distinguished on the one hand from Mammalia, and on the other from Ichthyopsida, or amphibians and fishes together. Aves are defined by the following characteristics: a body covered with feathers, a kind of exoskeleton no other animals possess; hot blood; completely double circulation; perfectly 4-chambered heart; single and dextral aortic arch; fixed lungs; air-passages prolonged into various airsacs, even into the interior of some of the bones of the skeleton; oviparous reproduction; eggs large and meroblastic, with copious food-yolk and albumen and a hard calcareous shell; limbs 4 in number, the anterior pair of which are modified as wings, and generally subserve flight by means of their large feathers, the distal segment of the limb being compressed and reduced, with not more than 3 digits, usually not unguiculate; the metacarpals more or less ankylosed as a rule, and the free carpals normally only 2 in adult life; a large breast-bone, usually carinate, and great pectoral muscles; numerous dorsolumbar, sacral, and urosacral vertebræ ankylosed into a sacrarium; ilia greatly produced forward, and ilia and ischia backward, normally without median symphyses; perforate cotyloid cavity; the trochanter of the femur articulating with an iliac antitrochanter, and the fibula incomplete below; the a tragalus ankylosed with the tibia, and assisting in forming the tibial condyles; mediotarsal anklejoint; not more than 4 metatarsals, 3 ankylosed together, and not more than 4 digits, the phalanges of which are usually 2, 3, 4, or 5 in number; the hind limb fitted as a whole for bipedal locomotion; and no teeth in any recent forms, the jaws being sheathed in horn. Birds have undergone little modification since their first appearance in the Jurassic age; their classification is consequently difficult, and no leading authors agree in detail. Liunæus (1766) divided them into 6 orders: Accipitres, Picæ, Anseres, Grallæ, Gallinæ, and Passeres. Cuvier's arrangement (1817) was similar, with the 6 orders Accipitres, Passerinæ, Scansores, Gallinæ, Grallæ, and Palmipedes. A system said to have been originally proposed by Kirby, and formerly much in vogue among English ornithologists, recognized Natatores, Grallatores, Cursores, Rasores, Scansores, Insessores, and Raptores as orders. The latest artificial system is that of Sundevall (1872-3), with the orders Oscines, Volucres, Accipitres, Gallinæ, Grallatores, Natatores, Proceres, and Saururæ, 42 subordinate groups, and 1,229 genera. In 1867 Huxley divided birds into 3 orders: Saururæ, Ratitæ, and Carinatæ; the latter into 4 suborders, Dromæognathæ, Schizognathæ, Desmognathæ, and Ægithognathæ, and 16 superfamily groups—an arrangement very different from any preceding one. The discovery of Odontornithes, or toothed birds, led to another primary division by Marsh into Odontolcæ, Odontotormæ, and Saururæ, this author not extending his classification to recent birds. In 1884 Coues divided all birds into 5 subclasses: Saururæ, with teeth, amphicælous vertebrac, carinate sternum, separate metacarpals, and long, lizard-like tail; Odontotormæ, with socketed teeth. biconcave vertebræ, carinate sternum, ankylosed metacarpals, and short tail; Odontolcæ, with teeth in grooves, heterocælous vertebræ, rudimentary wings, ratite sternum, and short tail; Ratitæ, without teeth, with heterocælous vertebræ, ratite sternum, rudimentary wings, ankylosed metacarpals, and short tail; Carinatæ, without teeth, with heterocælous vertebræ, carinate sternum, developed wings, ankylosed metacarpals, and short tail. The Carinatæ include all living birds, except the few struthious or ratite birds. For the carinate subclass or order, some 15 or 20 ordinal or subordinal groups are now usually adopted. One of these, Passeres, includes a large majority of all birds. The genera or subgenera of birds in use now range from about 1,200 to about 2,900. The species are usually estimated at about 10,000. See bird and Sauropsida.

GNU Webster's 1913

1. n. (Zoöl.) The class of Vertebrata that includes the birds.

WordNet 3.0

1. n. (ornithology) the class of birds