Final answer:
The two pronator muscles responsible for medially rotating the forearm and hand are the pronator teres and pronator quadratus, whereas the supinator is responsible for turning the forearm anteriorly.
Step-by-step explanation:
The two pronator muscles are the pronator teres and the pronator quadratus. They medially rotate the forearm and hand, allowing the forearm to be in the pronated position. In contrast, the supinator is the only muscle that turns the forearm anteriorly, which is supination. When the palm faces backward and the forearm is pronated, the radius and ulna form an X-shape, which is different from the parallel arrangement in the supinated position.