Clavicle
Long bone, part of the appendicular skeleton
Also known as: Collarbone
Classification
Long bone, part of the appendicular skeleton
Dimensions
Slender and S-curved, varying widely in length depending on the animal species, connecting the shoulder blade to the breastbone.
Key Features
Recognizable by its gentle, S-like curve and smooth, rounded ends. It looks like a miniature strut or brace, fairly delicate compared to limb bones.
Similar Bones
Can sometimes be confused with small ribs due to the curved shape. However, ribs typically feature a more uniform curve and articulating facets at both ends for connecting to the backbone and breastbone, whereas the collarbone features distinct, broadened ends for joint attachments.
Across Species
The collarbone varies wildly across the animal kingdom. Humans and climbing mammals have robust collarbones for flexible arm movement. Cats have a tiny, floating collarbone embedded in muscle, which allows their shoulders to tuck inward for squeezing through tight spaces and absorbing the impact of landings. Running specialists like horses and dogs have lost their collarbones entirely to allow longer, straighter strides focused strictly on forward motion.
Evolutionary History
The collarbone is an ancient structure, first appearing in early bony fish and primitive tetrapods as part of the shoulder girdle. Over millions of years, as various lineages adapted to specialized forms of locomotion—such as galloping versus grasping—this bone either strengthened into a stout strut or reduced into a tiny sliver.
Photography Tips
Place the bone on a neutral, solid-colored background with strong, even side-lighting to highlight the natural S-curve and surface contours. Include a small ruler or common coin next to the bone to show true scale.