Metatarsal
Long bone, part of the limb (appendicular) skeleton
Also known as: Hind cannon bone, shank bone, or mid-foot bone
Classification
Long bone, part of the limb (appendicular) skeleton
Dimensions
In large grazing mammals, this bone is typically elongated and straight, often being one of the longest bones in the lower leg. Its length is usually several times its width, providing significant height and leverage.
Key Features
Look for a long, straight shaft with a roughly circular or D-shaped cross-section. The upper end usually has a flat surface for meeting the ankle bones, while the lower end typically features a distinctive pulley-like shape or double-rounded knobs where it connects to the toes. A long groove often runs down the front or back of the shaft.
Similar Bones
This bone is frequently confused with the metacarpal (front cannon bone). Metatarsals are generally more square or angular in cross-section compared to the more rounded or oval front metacarpals. It can also be mistaken for a tibia, but it lacks the large, flaring triangular top and the sharp 'shin' ridge characteristic of the leg bone.
Across Species
In hoofed animals like deer, cows, and horses, the metatarsals have fused and lengthened over millions of years to create a single, sturdy 'cannon bone.' This allows them to run on their tiptoes, increasing stride length. In contrast, humans have five separate metatarsals that form the arch of the foot, while birds have a highly specialized, fused bone called a tarsometatarsus.
Evolutionary History
This bone represents a fascinating journey from the five-toed feet of early land vertebrates to the specialized, weight-bearing columns seen in modern ungulates. Over deep time, as many mammals moved from forests to open grasslands, the outer toes were often lost or reduced, and the central foot bones lengthened and fused to support high-speed running and efficient energy use.
Photography Tips
Place the bone on a neutral background and include a ruler or common object for size reference. Capture one photo from the front to show the full length, one from the side to show the profile, and clear close-up shots of both the top and bottom ends where the joints are located.