Metatarsals and Tarsals
Mixed collection including Long Bones (metatarsals) and Short Bones (tarsals) within the limb skeleton
Also known as: Foot bones, Instep bones, Ankle bones
Classification
Mixed collection including Long Bones (metatarsals) and Short Bones (tarsals) within the limb skeleton
Dimensions
The mid-foot long bones are typically slender and rectangular, while the blocky ankle bones vary from small cubes to a large, prominent heel-shaped structure.
Key Features
The assembly is recognizable by the way five long, thin shafts fan out from a cluster of chunky, interlocking blocks. The most distinctive part is the large, rounded block at the very back which forms a sturdy anchor point. The long bones have rounded heads at the front where they connect to the toe segments.
Similar Bones
The bones of the hand (metacarpals and carpals) are the most similar. However, foot bones are generally thicker and more robust to support weight. The heel bone is a unique giveaway—there is no equivalent large, protruding block in the wrist. Additionally, the mid-foot shafts are usually longer and flatter than the more rounded shafts found in the hand.
Across Species
The architecture of the foot varies wildly across the animal kingdom depending on how a creature moves. While humans have a flat-footed stance, dogs and cats walk on their toes (digitigrade), meaning these long mid-foot bones are essentially part of their lower leg. In horses, the middle bone has become incredibly thickened into a single 'cannon bone' to support high-speed running, with the other digits having largely disappeared through time.
Evolutionary History
These bones evolved from the fin-bases of lobe-finned fish that transitioned to land millions of years ago. Over deep time, the structure shifted from a flexible paddle to a rigid lever. In the lineage leading to modern terrestrial mammals, the heel bone lengthened to provide better leverage for muscles, allowing for efficient walking and upright standing.
Photography Tips
To help with identification, take one photo looking straight down at the top surface to show the fanning arrangement. Take a second shot from the side to capture the height of the ankle blocks and the arch. Including a common object like a coin or a ruler helps show the overall scale.