Metapodial (Metatarsal or Metacarpal)
Long bone, part of the appendicular skeleton
Also known as: Cannon bone, foot bone, lower leg bone
Classification
Long bone, part of the appendicular skeleton
Dimensions
Varies widely by species, ranging from a few inches in medium-sized mammals to over a foot in large grazing mammals, characterized by a straight, sturdy central shaft and wider ends.
Key Features
Look for a long, heavy shaft with a squarish or rounded cross-section. One end features a broad, blocky surface for joint connection, while the opposite end often shows a pulley-like shape with distinct ridges for toe or hoof attachment.
Similar Bones
Can be mistaken for other long limb bones like the upper arm bone or thigh bone. However, this bone tends to be much straighter with flatter surfaces along the shaft, lacking the dramatic twists, ball-shaped top ends, or deep offset knobs found near the shoulder and hip joints.
Across Species
In grazing animals like horses, these bones have fused and elongated into a single, massive support pillar to maximize running speed on open plains. In cloven-hoofed animals such as deer and cattle, two bones are fused together to handle heavy loads, while animals with nimble paws have separate, shorter bones for dexterity.
Evolutionary History
Over millions of years, mammalian foot bones underwent streamlining as ancestors moved from dense forests to open grasslands. Extra toes were lost or reduced, and the central bones lengthened and strengthened to create efficient, spring-like levers for high-speed running.
Photography Tips
Place the bone on a neutral, solid-colored background with a coin or ruler next to it for scale. Take one straight-down photo of the entire length, and a second photo focusing closely on the end surfaces to show the specific shape of the joint connections using soft, natural side-lighting.