Phalanx
Long bone, part of the appendicular skeleton
Also known as: Toe bone, finger bone, digit
Classification
Long bone, part of the appendicular skeleton
Dimensions
Typically small and slender, varying greatly in length and width depending on the specific digit and species, ranging from under an inch in small mammals to several inches in larger creatures.
Key Features
Look for a miniature long bone shape with one expanded, rounded end for forming a joint and a flatter, often notched opposite end. They are typically much smaller than arm or leg bones and have a gently curved profile.
Similar Bones
Can be easily confused with small metacarpals or metatarsals from the hands and feet. Phalanges are generally narrower and taper toward the ends, whereas palm and foot bones tend to be straighter and more uniform in thickness along the shaft.
Across Species
Digits vary wildly across the animal kingdom. In humans and many land mammals, they are designed for gripping or walking. In horses, the entire weight of the animal rests on the tip of a single heavily modified phalanx enclosed in a hoof. In whales and dolphins, these bones are multiplied within broad flippers to form paddle-like structures. In birds, they are elongated and fused within the wing and foot to support flight and perching.
Evolutionary History
The basic pattern of multiple tiny bones making up the ends of limbs dates back to the earliest tetrapods that crawled out of the ancient Devonian waters. Over hundreds of millions of years, these modular elements have been stretched, fused, reduced, or multiplied to suit everything from burrowing and running to swimming and flying.
Photography Tips
Place the bone on a solid, neutral-colored background with a coin or ruler next to it for scale. Use bright, even lighting from the side to bring out the contours of the joint ends, and take your main shot directly from above.