Humerus
Long Bone, part of the appendicular skeleton
Also known as: Upper Arm Bone
Classification
Long Bone, part of the appendicular skeleton
Dimensions
Varies widely by species, featuring a sturdy cylindrical shaft connecting two distinct ends with specialized joining surfaces.
Key Features
Look for a long, straight or gently curved shaft with one rounded, bulbous end for a ball-and-socket joint, and an opposite end flattened or grooved to form a hinge.
Similar Bones
Can be confused with the femur or the lower leg bones. Unlike the femur, which usually has a distinct offset ball at the top, this bone typically features a more centered head and a twisted shaft.
Across Species
In birds, this bone is often lightweight and hollow to assist with flight, while in marine mammals like whales, it is shortened and stout. In running mammals, it is built for endurance and speed.
Evolutionary History
Tracing its origins back to the paired fins of ancient lobe-finned fish, this bone evolved to support weight-bearing locomotion on land, transitioning from an aquatic paddle into a versatile limb segment.
Photography Tips
Place the bone on a neutral, non-reflective background with a coin or ruler for scale. Use soft, directional lighting to highlight the contours of the ends and take photos from both the top and bottom angles.