Which muscle covers the top of the head?

The muscle that covers the top of the head is the frontalis. This muscle is part of the epicranius (or occipitofrontalis), which is a broad muscle that also includes the occipitalis at the back of the head. The frontalis specifically is located at the forehead and is responsible for raising the eyebrows and wrinkling the forehead, contributing to facial expressions.

The reason the epicardium is not the correct choice is that it refers to the outer layer of the heart, not a muscle associated with the head. Similarly, while the occipitalis is a muscle that contributes to the scalp at the back of the head, it does not cover the top. The temporalis muscle is located on the side of the head and functions mainly for chewing, also not covering the top of the head. Thus, the frontalis is the appropriate muscle associated with the area described in the question.