Mastication Muscles in Hoary Fox (Lycalopex vetulus - LUND, 1842): Descriptive and Comparative Study

Mastication muscles are responsible for lowering and elevation of mandible, which four of them are responsible for mandible elevation in Hoary Fox: Masseter, Temporal, Medial Pterygoid and Lateral Pterygoid; and one for lowering: Digastric. Considering anatomical study of these muscles, the present work aimed to describe, analyze and compare the anatomy of Hoary Fox mastication muscles with data described in literature. In this sense, for this work development, two specimens of Hoary fox (Lycalopex vetulus) were used, being fixed in aqueous solution of 10% formaldehyde for conservation, with later description of characteristics, location, size, origin and insertion of muscles. Thus, was observed that Masseter muscle of Hoary Fox is relatively smaller than other species, such as Capuchin Monkey. A slight protuberance was also observed on lateral surface of the face, covering Ramus and Angle of mandible. When analyzed, Medial Pterygoid Muscle is a robust muscle and originates from Palatine and Pterygoid bones, directing dorsocaudally for insertion into medial face of the angle of mandible and adjacent areas, a location that is confused with Masseter (superficial part) insertion. Lateral pterygoid muscle is considerably smaller than medial and extends from sphenoid bone to mandible branch. Temporal muscle is the largest muscle of Hoary Fox head, composed of four parts: Dorsal, Medial, Ventral and Rostral; this muscle has its surface face covered by a thick fascia, the Temporal Aponeurosis.