Ischium Ischium The ischium () forms the lower and back part of the hip bone ("os coxae"). Situated below the ilium and behind the pubis, it is one of these three bones whose fusion creates the hip. The superior portion of this bone forms approximately one third of the acetabulum. The ischium is made up of three parts–the body, the superior ramus and the inferior ramus. The body contains a prominent spine, which serves as the origin for the superior gemellus muscle. The indentation inferior to the spine is the lesser sciatic notch. Continuing down the posterior side, the ischial tuberosity
Aphanosauria bone, although perhaps a small portion was open according to a notch near where the ischium contacts the illium (upper blade of the hip). The gracile femur (thigh bone) of aphanosaurs possesses a characteristic set of features which can be used to diagnose the group. The proximal (near) surface of the bone, which connects to the hip socket, has a deep groove on it, rather than simply being a flat articulation surface. In addition, the bone's distal (far) articulation, which connects to the lower leg bones, is concave. The proximal part of the femur also has several bumps (tubers) on