Furcula
Part of the appendicular skeleton, the furcula is a specialized structure formed by the fusion of two collarbones (clavicles).
Also known as: Wishbone, Furca, Merrythought
Classification
Part of the appendicular skeleton, the furcula is a specialized structure formed by the fusion of two collarbones (clavicles).
Dimensions
The size varies greatly depending on the bird species, from less than an inch in small songbirds to several inches in large fowl like turkeys. It typically has a 'V' or 'U' shape with two long arms meeting at a central point.
Key Features
The most defining feature is its symmetrical 'V' or 'Y' shape. The two branching arms have slightly flattened or rounded tips where they connect to the shoulders, and the bottom 'crotch' of the V often features a small, projecting plate or 'keel' that points toward the bird's chest.
Similar Bones
It can sometimes be confused with the lower jawbone (mandible) of small mammals or reptiles. However, the furcula is usually much thinner, lighter, and more elastic, lacking the tooth sockets or complex hinge joints found on a jawbone.
Across Species
While humans and many mammals have two separate collarbones, birds have fused theirs into this single, spring-like structure. In strong flyers, the furcula is robust and acts like a spring that stores and releases energy during a wingbeat. In some flightless birds like ostriches, the collarbones may not be fused at all. Interestingly, this bone is not unique to modern birds; it has been found in many theropod dinosaurs, including the Tyrannosaurus rex.
Evolutionary History
The furcula first appeared in two-legged, meat-eating dinosaurs long before the first birds took to the skies. Originally, it may have helped these predators handle struggling prey, but over millions of years, it was repurposed to support the heavy chest muscles required for flight, proving to be a key innovation in the transition from dinosaurs to birds.
Photography Tips
Lay the bone flat on a neutral background to show the full 'V' shape from above. It is also helpful to take a side-on photo to show the curvature of the arms and the projection of the central keel. Including a coin or a ruler in the frame is essential for showing its size.