Furcula
Irregular bone; part of the core skeleton in birds
Also known as: Wishbone, Merrythought
Classification
Irregular bone; part of the core skeleton in birds
Dimensions
Generally a slender, V-shaped or U-shaped structure. Its size varies significantly depending on the bird's wingspan, ranging from less than an inch in songbirds to several inches in large fowl.
Key Features
It looks like a fork with two thin, curving arms that meet at a central point or 'knob.' One end of each arm is usually flattened for shoulder attachment, while the bottom junction often has a small, protruding plate that points toward the belly.
Similar Bones
It can be confused with the lower jaw of some small reptiles or the pelvic bones of very small mammals. However, the wishbone is distinct because it is usually a single, fused piece of bone with a signature symmetrical 'V' shape and lacks any teeth or deep circular hip-sockets.
Across Species
The furcula is a unique feature of birds and their feathered dinosaur ancestors. While mammals have two separate collarbones that connect the shoulders to the breastbone, in birds, these two bones are fused at the bottom to create a flexible spring. For instance, in a turkey, the bone is thick and rigid to support a heavy body, whereas in high-speed flyers like swifts, it is thin and highly elastic to act as a bellows during flight.
Evolutionary History
This bone provides a direct link between modern birds and theropod dinosaurs. Ancient fossilized relatives of the T-Rex possessed primitive versions of these fused bones. Over millions of years, as these lineages took to the skies, the bone evolved from a simple chest support into a specialized 'spring' that helps store and release energy during every wing beat.
Photography Tips
To identify a wishbone, lay it flat on a plain surface and take a photo from directly above to show the overall curve. Then, take a close-up of the bottom junction where the two arms meet, as the shape of this 'point' is a key clue for determining different bird families.