Humerus
Long bone of the appendicular skeleton
Also known as: Upper Arm Bone
Classification
Long bone of the appendicular skeleton
Dimensions
Varies widely by species, from a few inches in small mammals to over a foot in larger quadrupeds, characterized by a slender middle shaft and larger, shaped ends.
Key Features
Recognizable by its long, gently curved central shaft, a rounded ball-like shape at one end for joint movement, and a spool-shaped or flared pulley structure at the opposite end.
Similar Bones
Can be confused with the femur or thigh bone. The humerus generally features a more distinct, rounded ball at the top and a different pulley design at the bottom compared to the longer, straighter femur.
Across Species
In running animals like horses and deer, the humerus is short and heavily tucked into the shoulder muscles for powerful strides. In burrowing animals, it becomes stout and wide to anchor heavy digging muscles. In birds, it connects to the wing and is often hollow and light to aid in flight.
Evolutionary History
Originating from the paired fins of ancient lobe-finned fish, the humerus has spent hundreds of millions of years adapting from a paddle-like prop into a versatile lever capable of walking, running, swimming, and flying.
Photography Tips
Place the bone on a plain, neutral background with a ruler or coin next to it for scale. Take one shot showing the entire bone from the top down, and additional close-up shots of both ends to highlight the unique joint shapes.