The middle of this is termed the cotyloid fossa.

Arising from the cotyloid fossa and connecting to the femoral head lies the ligamentum teres.

The anatomical exception was that in the upper region of the dinosaur's femur a hinged joint occurred in the cotyloid cavity, implying that the leg could be moved forwards and backwards.

The acetabular labrum (glenoidal labrum of the hip joint or cotyloid ligament in older texts) is a ring of cartilage that surrounds the acetabulum (the socket of the hip joint).