Final answer:
The pronator quadratus muscle originates on the ulna and inserts on the radius distally. It works together with other muscles to pronate the forearm.
Step-by-step explanation:
The pronator quadratus muscle has its origin on the ulna and its insertion on the radius, specifically on the distal 1/4 of the radius. The pronator quadratus muscle is located in the forearm and is responsible for pronating the forearm, turning it so that the palm faces downward. It works together with other muscles such as the pronator teres to achieve this movement.