Metapodials (specifically a Metacarpal or Metatarsal)
Long Bone; part of the limb (appendicular) skeleton
Also known as: Cannon bone, shank bone, or foot bone
Classification
Long Bone; part of the limb (appendicular) skeleton
Dimensions
Variable by species; in hooved animals, these are typically long and slender, often making up a significant portion of the lower leg length. They can range from a few inches in small deer to over a foot in large cattle.
Key Features
The most identifying feature is the 'pulley' or spool-like joint at the bottom end, which often has a distinct notch in the middle. The shaft is generally straight and may have a long groove running down the front or back, marking where two bones became one. The top end is usually flat or slightly dished where it meets the ankle or wrist.
Similar Bones
This can be confused with a humerus (upper arm) or femur (thigh), but those bones have rounded, ball-like joints at the top and are much thicker. It may also look like a radius (forearm), but the radius is often flatter and lacks the very specific double-pulley joint at the bottom.
Across Species
In many four-legged mammals like deer, cows, and sheep, two separate foot bones have fused over millions of years into a single, sturdy 'cannon bone' to provide strength for running. In contrast, humans have five separate palm or arch bones, and pigs have four distinct toes that remain mostly separate. This specific bone shows a 'pulley' shape at the bottom, which is a classic trait of even-toed animals known as artiodactyls.
Evolutionary History
This bone tells the story of terrestrial locomotion. Early mammals had multiple small bones in their feet to navigate uneven terrain. As some lineages moved toward open grasslands, their feet became specialized for speed. Through deep time, the outer digits were lost or reduced, and the central bones lengthened and fused to form a rigid pillar, allowing for an efficient, spring-like stride.
Photography Tips
Place a common object like a coin or a ruler next to the bone to show its size. Take one clear photo from the front, one from the side, and a close-up of both the top and bottom joints, as these end pieces are the 'fingerprints' of the bone.
Notes
Found in cemetary