Metatarsals
Long bones of the limb (appendicular) skeleton
Also known as: Midfoot bones, instep bones
Classification
Long bones of the limb (appendicular) skeleton
Dimensions
These are five slender, rod-like bones. The first one, located on the inner side, is typically the thickest and strongest, while the others are longer and more delicate in comparison.
Key Features
Each bone has a squared-off base at the back of the foot, a long shaft, and a rounded, marble-like head at the front end where the toes attach. When grouped together side-by-side, they form a natural bridge or arch that is easily recognizable.
Similar Bones
They are most often confused with the metacarpals of the hand. You can tell them apart because the metatarsals of the foot are generally more flattened from side to side and have more irregular, blocky bases compared to the more rounded bases found on the hand bones.
Across Species
In nature, these bones vary wildly based on habitat. In horses, the middle metatarsal has become a massive 'cannon bone' to support high-speed running, while the others have dwindled. In birds, they are often fused into a single strong structure called the tarsometatarsus. In aquatic mammals like seals, they are flattened and elongated to support the fleshy webbing of their flippers.
Evolutionary History
These bones evolved from the basic limb patterns of early four-legged land animals (tetrapods). Over millions of years, as our ancestors transitioned from climbing trees to walking upright on the ground, these bones shifted from a flexible, fan-like arrangement to a more rigid, arched structure that acts like a springboard for efficient travel.
Photography Tips
To capture these bones clearly, take a photo from directly above the top of the foot and another from the side to show the curve of the arch. Using a soft light from the side can help highlight the ridges of the shafts under the skin. Placing a ruler next to the foot provides a great size reference for your field notes.