Final answer:
The prime mover in the protraction of the scapula is the serratus anterior, a muscle located on the anterior thorax responsible for allowing lateral and forward movement of the scapula.
Step-by-step explanation:
The muscle that is the prime mover in the protraction of the scapula is the serratus anterior. This muscle is located on the anterior side of the thorax and plays a crucial role in the movement of the scapula, allowing it to move laterally and forward along the thoracic wall. It is different from the pectoralis minor, which also assists in scapular motion but is not the prime mover in protraction.