Clavicle
Long bone of the appendicular skeleton
Also known as: Collarbone
Classification
Long bone of the appendicular skeleton
Dimensions
Varies widely by species, typically slender and elongated with a gentle S-curve, connecting the breastbone to the shoulder blade.
Key Features
Look for a distinct S-shaped or crank-like curve along the main shaft, with one flattened wide end and one rounded or knob-like end.
Similar Bones
Can sometimes be confused with small ribs due to the gentle curve, but ribs are usually more uniformly curved like a bow and feature distinct grooves and articular facets not found on this bone.
Across Species
The clavicle varies immensely across mammals. Humans and climbing primates have robust clavicles for wide shoulder mobility and arm swinging. Running mammals like horses and dogs have completely lost or reduced their clavicles to a tiny splinter of bone, locking their front limbs into a stable front-to-back swinging motion for efficient galloping.
Evolutionary History
The clavicle is one of the oldest bones in the vertebrate skeleton, originating in early bony fish and prehistoric tetrapods as part of the shoulder girdle. It has frequently been reduced or lost entirely in animal lineages that specialized in running or swimming rather than grasping and climbing.
Photography Tips
Place the bone on a solid, neutral background with a coin or ruler nearby for scale. Capture a top-down view showing the full S-curve and another shot focusing on the shape of both ends.