What type of synovial joint consists of an elliptical convex head fitting into an elliptical concave socket?

The correct choice describes the ellipsoidal synovial joint, which is characterized by an elliptical convex surface fitting into an elliptical concave surface. This configuration allows for a variety of movements, particularly flexion and extension, as well as some degree of side-to-side movement (abduction and adduction) and rotation.

Ellipsoidal joints are found in locations such as the wrist, where the radius articulates with the carpal bones. The shape of the joint allows for smoother movements and more versatility compared to other joint types.

In contrast, hinge joints allow movement primarily in one plane (flexion and extension) and do not facilitate the same range of motion. Saddle joints also permit movement in two planes, but their structure differs in that each articulating surface is concave in one direction and convex in the other, resembling a saddle. Ball and socket joints, while they provide a wide range of motion, consist of a round head fitting into a cup-like socket, which is not the case with ellipsoidal joints. Thus, the definition and characteristics of the ellipsoidal joint make it the correct answer in this context.