Distal Phalanx
Short bone, part of the limb (appendicular) skeleton
Also known as: Claw core, toe bone, or coffin bone
Classification
Short bone, part of the limb (appendicular) skeleton
Dimensions
In typical small mammals, these are quite small, often measuring under an inch in length. They are characterized by a wide base and a tapering, curved point.
Key Features
Look for a pointed, slightly curved shape resembling a small horn or a thorn. It typically features a flat or slightly concave base where it connects to the rest of the toe, often with a small bump or 'hood' near the base where the claw sheath attaches.
Similar Bones
This can be confused with a small tooth or a thorn. However, a tooth will have a smooth enamel coating on the crown, whereas this bone has a porous, textured surface. Unlike a plant thorn, it will have a distinct joint surface at the wide end for connection with the middle toe bone.
Across Species
While these function as the bony core for claws in carnivores like cats and raccoons, they take on vastly different forms in other species. In horses, the same bone is large and spade-shaped, known as the coffin bone, providing the foundation for the hoof. In birds, it is the sharp core within the talons used for gripping prey.
Evolutionary History
These bones evolved from the simple bony tips of the digits in early land-dwelling vertebrates. Over millions of years, they specialized into diverse forms suited for climbing, digging, or running. In predatory mammals, they developed a distinct curve and a specialized groove to support the keratin sheath of a sharp claw.
Photography Tips
Place the object on a flat, neutral background next to a coin or a ruler for scale. Capture one photo from the top looking down and a second photo from the side to show the degree of curvature and the shape of the base.