PSM V42 D703 Left carpo metacarpus from the hand of an extinct swan

The carpometacarpus is a bone found in the hands of

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

. It results from the fusion of the

carpal The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, th ...

and

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...

bone, and is essentially a single fused bone between the

wrist In human anatomy, the wrist is variously defined as (1) the Carpal bones, carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known ...

and the

knuckle The knuckles are the joints of the fingers. The word is cognate to similar words in other Germanic languages, such as the Dutch "knokkel" (knuckle) or German "Knöchel" (ankle), i.e., ''Knöchlein'', the diminutive of the German word for bone (' ...

s. It is a smallish bone in most birds, generally flattened and with a large hole in the middle. In

flightless bird Flightless 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 In ...

s, however, its shape may be slightly different, or it might be absent entirely. It forms the tip of the

wing 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 expres ...

skeleton in

. To it, most of the primary

remiges 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 (), singular remex (), while those on the tail ...

attach. The

alula The alula , or bastard wing, (plural ''alulae'') is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ''ala'', meaning "wing". The al ...

, by contrast, is formed by the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

, which does not completely fuse with the other hand-bones. Likewise, the tipmost primaries attach to the

phalanx bone The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

To non-

biologists A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual cell, a multicellular organism, or a community of interacting populations. They usually specialize in a ...

the carpometacarpus may be best known from

buffalo wings A Buffalo wing in American cuisine is an unbreaded chicken wing section ( flat or drumette) that is generally deep-fried and then coated or dipped in a sauce consisting of a vinegar-based cayenne pepper hot sauce and melted butter prior to serv ...

. Buffalo wings come in two basic sizes, a large angled one containing three major bones, and a smaller flat one containing only two. The bone missing in the latter is the carpometacarpus.

References

* Bird anatomy {{Vertebrate anatomy-stub

See also

References