Final answer:
The anterior gluteal muscles attached to the ilium are laterally rotated in bipeds, facilitated by muscles such as the gluteus maximus, medius, and minimus which originate on the pelvic girdle and insert on the femur to support movement and stability.
Step-by-step explanation:
The anterior gluteal muscles, which attach to the ilium, are rotated laterally in the biped. This lateral rotation is facilitated by several muscles in the gluteal region, including the gluteus maximus, gluteus medius, and gluteus minimus, as well as other muscles like the piriformis and the obturator internus. These muscles originate on the pelvic girdle and insert on the femur, acting to extend, abduct, and laterally rotate the thigh at the hip. The powerful gluteus maximus, aided by the tensor fascia lata, also contributes to this action by pulling on the iliotibial tract, making it taut. If the pelvic girdle had the same range of motion as the pectoral girdle, which is not the case, stability and energy efficiency during walking would be compromised due to the increased mobility leading to less secure placement of the femurs in the acetabula of the pelvis.