Fox facial and masticatory muscles
Photo and text: Nick Zolkowski and Elizabeth Farrell
Left lateral view of the fox head; rostrum to the bottomof the photo; external ear (pinna) removed.
During the skinning process the superficial muscles of expression, including the platysma and orbicularis oris, were removed, leaving only the masticatory muscles for dissection. The facial muscles which we located, the masseter and the temporalis, are the primary muscles of mastication and work in conjunction with each other. The temporalis begins closing the jaw, and the action is then transferred to the masseter [1]. The fox is a predator that uses its jaws in a powerful snapping motion to subdue its prey. To enable such power, the angle between the upper and lower jaw must be large. Further, the muscles associated with closing the jaws need to be relatively robust, especially the temporalis. Mammals not needing to bite at such a gape, such as rabbits, which chew food rather than forcefully bite, have a much less massive temporalis. In the fox, the masseter and temporalis muscles are similar in length and thickness, with the temporalis being a little more expansive in surface area.
As the lateral aspect of the head was covered in a layer of thick fascia, we experienced difficulty in exposing the masseter and the zygomatic arch. The masseter originates on the zygomatic arch and inserts on the masseteric fossa of the mandible. As we did not transect the masseter, we did not observe the insertion, although we were able to probe it. The majority of the temporalis muscle lies superior to the zygomatic arch. Its origins are the sagittal, frontal, and nuchal crests of the cranium and the zygomatic arch, and it inserts on the coronoid process of the dentary. As it approaches its insertion the temporalis muscle runs deep to the zygomatic arch and the masseter muscle.
1.Alderton, David. 1994. Foxes, Wolves, and Wild Dogs of the World. Facts on
File, New York.