Clavicle
Long bone (with a modified flat structure), part of the appendicular skeleton
Also known as: Collarbone
Classification
Long bone (with a modified flat structure), part of the appendicular skeleton
Dimensions
Typically ranges from 10 to 15 centimeters in length for humans, featuring a gentle S-curve shape that acts as a structural strut between the breastbone and the shoulder blade.
Key Features
Easily recognized by its distinct horizontal S-curve, smooth rounded shaft, and flattened, slightly expanded ends where it connects to neighboring bones.
Similar Bones
Can sometimes be confused with small ribs due to the curved shape, but unlike ribs, the collarbone lacks a deep internal groove and has a much more rigid, twisted contour.
Across Species
The clavicle varies wildly across the animal kingdom. Humans and climbing mammals like primates have robust collarbones to support flexible, wide-ranging arm movements. Running mammals like horses and dogs have lost or greatly reduced their clavicles to allow their front legs to swing strictly back and forth for speed.
Evolutionary History
The collarbone is one of the oldest skeletal structures in vertebrate history, originating in early bony fish and primitive tetrapods as part of the shoulder girdle. Over millions of years, it has transformed from a broad, protective plate of armor into a specialized strut that helps stabilize the shoulder joint.
Photography Tips
Photograph the bone flat against a neutral background from top-down and profile views. Use bright, even lighting to highlight the curved contours and include a coin or ruler for scale.