Metapodial
Long bone belonging to the appendicular skeleton
Also known as: Cannon Bone or Foot Bone
Classification
Long bone belonging to the appendicular skeleton
Dimensions
Typically elongated and remarkably straight, varying widely from a few inches in smaller mammals to over a foot in large grazing animals, maintaining a slender central shaft with broader, flattened ends.
Key Features
Look for a remarkably straight, tubular central shaft that feels heavy and dense, featuring smooth surfaces on the outer side and squared-off, blocky ends where joints once connected.
Similar Bones
Can be mistaken for a radius or ulna, but those forearm bones usually display a distinct curve and work in pairs, whereas this foot bone is solitary, exceptionally straight, and remarkably sturdy for its length.
Across Species
In grazing animals like horses and deer, this bone is heavily fused and elongated to act as an extra lever for speed and bounding strides. In creatures with splayed feet or digging habits, such as bears or rodents, these bones remain separate and much shorter to allow for flexibility and gripping power.
Evolutionary History
Over millions of years, ancestors of modern hoofed mammals saw a reduction in the number of individual toe and foot bones. These separate elements merged and elongated into a single, highly sturdy pillar designed to withstand the tremendous impact forces of running across open plains.
Photography Tips
Place the bone on a solid, neutral-colored background with a coin or ruler next to it for scale. Take one straight-down top view to show its overall length and straightness, and another close-up of the wide end to reveal the joint surface texture.