Which of the following is an example of an irregularly shaped bone?

The sesamoid bones are classified as irregularly shaped bones due to their unique structure and function. These bones typically develop within tendons and are not part of the traditional long, short, flat, or sesamoid categories. They often serve to protect tendons from stress and wear, as well as to improve the mechanical advantage of the muscles that act on the joint.

In contrast, the femur and radius are long bones, primarily characterized by their elongated shape, which contributes to their role in supporting weight and facilitating movement. The scapula, while it has a somewhat irregular shape, is generally classified as a flat bone because of its broad, flat surface that contributes to the mechanics of shoulder movement. Therefore, the sesamoids stand out as the best example of an irregularly shaped bone among the options provided.