Metatarsal (Fragment)
Long Bone (Appendicular skeleton)
Also known as: Hind cannon bone, shank bone, or lower leg bone
Classification
Long Bone (Appendicular skeleton)
Dimensions
In typical large hoofed mammals, these are elongated and straight. The central shaft is often robust and roughly square or D-shaped in cross-section to support weight. Total length varies greatly between species, ranging from a few inches in small deer to over a foot in cattle or moose.
Key Features
Look for a long, straight shaft with a very thick outer wall and a hollow center. A primary identification cue for many grazing animals is the 'vascular groove'—a long, shallow vertical indentation running down the flat face of the bone. The texture is often very dense and smooth compared to ribs or vertebrae.
Similar Bones
This is most often confused with the Metacarpal (front leg bone). You can tell them apart by the cross-section: the front version is usually more D-shaped or flat on the back, while the hind version shown here tends to be more square or angular in shape. It may also be mistaken for a portion of a Femur, but the Femur is much rounder and lacks the deep vertical groove found here.
Across Species
Hoofed mammals have highly specialized lower legs. In horses, the middle metatarsal is the only functional leg bone below the ankle, while the outer ones have shrunk into small 'splints'. In deer and cattle, two main segments have fused into a single strong tube with a characteristic groove down the front. This design provides incredible strength for running and supporting heavy body mass without adding much weight.
Evolutionary History
This bone shows the progression from five-toed ancestors to modern specialists. Over millions of years, as grazing animals moved into open grasslands, their side toes lifted off the ground and eventually disappeared. The remaining central bones became longer and fused together, acting like a built-in pogo stick that increases stride length and energy efficiency during locomotion.
Photography Tips
Place a common object like a coin or a ruler next to the piece to show its size. Take photos from several angles: one looking straight at the flat 'face,' one from the side to show the profile, and most importantly, a clear shot looking directly into the hollow end to see the thickness of the bone wall.