Metapodial
Long bone, part of the appendicular skeleton
Also known as: Cannon Bone or Foot Bone
Classification
Long bone, part of the appendicular skeleton
Dimensions
Typically ranges from several inches to over a foot in length depending on the animal, featuring a straight, robust shaft with broadened, sculpted ends designed to bear heavy weight.
Key Features
Look for a remarkably straight, thick-walled cylindrical shaft flanked by squared-off, blocky ends with distinct grooves and ridges for joint connections. It lacks the twists and complex curves found in upper limb bones like the upper arm or thigh bones.
Similar Bones
Can be easily confused with the upper arm bone or the shin bone. However, this bone is typically much straighter and more symmetrical from top to bottom, lacking the prominent ball joint or sharp crests found on other major limb elements.
Across Species
In grazing animals like horses and deer, this bone is greatly elongated and fused to act as an extra leg segment, adding incredible spring and length to the stride. In bears and humans, the equivalent bones remain separate and much shorter, forming the structure of the palm or sole.
Evolutionary History
Over millions of years, hoofed mammals underwent a dramatic evolutionary reduction in their number of toes. Their foot bones stretched out and consolidated into single, highly efficient weight-bearing columns to maximize running speed across open plains.
Photography Tips
Place the bone against a neutral background with a ruler or coin next to it for scale. Take one straight-down top view showing the full length, and close-up profile shots of both ends to clearly display the joint surfaces.