Furcula
Irregular Bone; part of the limb (appendicular) skeleton in birds.
Also known as: Wishbone, Merrythought
Classification
Irregular Bone; part of the limb (appendicular) skeleton in birds.
Dimensions
This bone typically resembles a 'V' or 'U' shape, with two slender arms meeting at a central point. Size varies greatly by bird species, from less than an inch in songbirds to several inches in large waterfowl or turkeys.
Key Features
The most defining feature is the central junction where the two arms meet, often featuring a flattened, paddle-like protrusion. The arms themselves are often curved and elastic-looking, ending in flattened plates that connect to the shoulder area.
Similar Bones
It is most often confused with the lower jawbone of a small mammal. However, a jawbone will usually have small sockets for teeth or a more complex hinge at the ends, whereas the wishbone is a single, continuous unit without tooth-bearing surfaces.
Across Species
Unique to birds and certain dinosaurs, the furcula is formed by the fusion of the two collarbones. In strong flyers like eagles, it is rigid and wide to support powerful wing strokes, while in flightless birds like ostriches, the two sides may not even meet or fuse, remaining as separate small bones.
Evolutionary History
While once thought unique to birds, we now know this bone first appeared in meat-eating dinosaurs (theropods). It functioned as a structural brace for the chest long before birds took to the skies, and later evolved to act like a spring, storing energy during the flapping motion.
Photography Tips
Lay the bone flat on a plain background with a coin or ruler next to it for size reference. Take one photo looking straight down at the 'V' shape and another from the side to show the curve and the central point's thickness.