Hip bone muscles. Monotremes and marsupials also possess a fourth pair of bones, the prepubes or "marsupial bones", which extend forward from the pubes, and help to support the abdominal muscles and, in marsupials, the pouch. In placental mammals, the pelvis as a whole is generally wider in females than in males, to allow for the birth of the young. The pelvic bones of cetaceans were formerly considered to be vestigial, but they are now known to play a role in sexual selection. Hip bone The hip bone (os coxa, innominate bone, pelvic bone or coxal bone) is a large flat bone,
Muscles of the hip the tibia/fibula, have a large moment assisting with hip extension. Movements of the hip occur because multiple muscles activate at once. Most muscles are also responsible for more than one type of movement. Movements of the hip are described in anatomical terminology using anatomical terms of motion. The movement that brings the thighs close to the abdomen is called "flexion". When the legs open, such as in the lotus posture of yoga, this is called "lateral rotation", with the opposite movement called "medial rotation". Hip abduction occurs when the femur moves outward to the side, as in taking the thighs