Phalanx
Long bone of the limb skeleton (specifically the hand or foot).
Also known as: Toe bone, Finger bone, or Digit bone
Classification
Long bone of the limb skeleton (specifically the hand or foot).
Dimensions
In mammals, these are generally small and rectangular with widened ends compared to the middle shaft. Their length and thickness vary based on the animal's size and whether they belong to the front or back limb.
Key Features
It looks like a miniature version of a limb bone, featuring a narrower middle and two wider, rounded ends. One end usually has a shallow indentation like a cup, while the other end has a smooth, rounded surface shaped like a spool or a double-bump that allows it to hinge with the next bone in the series.
Similar Bones
It is often confused with the metacarpal or metatarsal bones (those in the palm or arch of the foot). However, phalanges are generally shorter and lacks the more complex, squared-off base found on the palm bones that connect to the wrist or ankle.
Across Species
In nature, this bone is a master of adaptation. In deer and cows, the phalanges support sharp hooves for running over hard ground. In bats, they have evolved into incredibly long, thin structures that support the wing membrane. In whales, these bones are encased in fleshy flippers, while in humans and other primates, they remain flexible to allow for grasping and tool use.
Evolutionary History
These bones developed from the fin rays of ancient lobe-finned fish as they transitioned to life on land. Over millions of years, the typical five-digit pattern emerged in early tetrapods. In many modern lineages, such as horses, some digits were lost or fused to increase speed, while in mammals like us, the bones retained a generalized structure for versatile movement.
Photography Tips
Lay the bone against a flat, neutral background. Take one photo from directly above to show the general silhouette, and another from the side to capture the curve of the shaft. Including a common object like a coin or a ruler helps show scale.