Sternopygus Müller & Troschel, 1849

Peixoto, Luiz Antônio Wanderley & de Pinna, Mário, 2022, Patterns of diversification and phylogenetic structure in the dorsolateral head musculature of Neotropical electric eels (Ostariophysi: Gymnotiformes), with a myological synonymy, Neotropical Ichthyology (e 210009) 20 (1), pp. 1-117 : 49

Sternopygus Müller & Troschel, 1849

Adductor mandibulae. The rictalis originates in the quadrate, sympletic, and hyomandibula. The lateralmost fibers of the ventral portion of the rictalis is restricted to the anterior margin of the preopercular fossa. That section inserts solely on the coronoid process, with some lateralmost fibers associated with the buccopalatal membrane. The stegalis arises from the hyomandibula, sphenotic, pterosphenoid, metapterygoid, and quadrate; and converges into the meckelian tendon which, in turn, inserts on the coronomeckelian bone, with some anterodorsal fibers converging to the mandibular tendon. The stegalis is located laterally in relation to the basal region of the endopterygoid, overlapping it completely; except in S. xingu , in which the stegalis overlaps only the posterior portion of the basal region of the bone. Normally, the stegalis overlaps only the ventral portion of the adductor arcus palatini, except in S. xingu , where the stegalis is positioned laterally only to the mid-posterior portion of the adductor arcus palatini, overlapping it partially.

The segmentum mandibularis is located dorsally to Meckel’s cartilage, extending about 80% of the dorsal portion of this cartilage. The course of the ramus mandibularis trigeminus nerve is lateral to the stegalis and mesial to the rictalis and malaris.

Levator arcus palatini. The levator arcus palatini has a roughly parallelogram shape, originating from the ventral margin of the frontal, pterosphenoid, and sphenotic and inserting onto the hyomandibula. The origin of the levator arcus palatini is equal to its insertion (Peixoto, Ohara, 2019: fig. 13B). At the insertion of the levator arcus palatini, all fibers are located laterally to the malaris (except for one specimen of S. macrurus , with the posteromedial fibers mesial to the malaris); and with only the posterodorsal fibers being mesial to the dilatator operculi, where the anterior margin of the dilator operculi does not exceeds the medial portion of the levator arcus palatini. The generalized pattern consists of a strictly fibrous composition of levator arcus palatini, however, some more mesial tendons ossify in S. xingu , resulting in the occurrence of intermuscular bones.