Hypopomus Gill, 1864

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 : 33-34

Hypopomus Gill, 1864

Adductor mandibulae. The malaris originates from the mid-dorsal portion of the hyomandibula and preopercle. Its insertion occurs on the posteromedial portion of the antorbital bone by a fibrous attachment, with its mesialmost fibers converging onto a small endomaxillary ligament, less than one-third the length of the malaris which, in turn, inserts on the posteromedial portion of the maxilla ( Fig. 4 ). The rictalis originates in the preopercle, sympletic, quadrate, and hyomandibula. The lateralmost fibers of rictalis surpass the anterior margin of the preopercular fossa and reach the mid-portion of the preopercle; with the posterodorsal fibers almost reaching the posterior margin of that bone. That subsection inserts on the coronoid process.

The stegalis arises from the sphenotic, pterosphenoid, metapterygoid and anterior margin of the hyomandibula. Towards its insertion, the fibers of stegalis differentiates into an intersegmental aponeurosis, dorsally entering the mandibular tendon and ventrally the meckelian tendon which, in turn, inserts onto the coronomeckelian bone ( Fig. 4 ). The stegalis is located laterally in relation to the basal region of the endopterygoid and adductor arcus palatini, overlapping those structures completely.

The segmentum mandibularis is located dorsally to Meckel’s cartilage and does not contact directly the dorsal margin of Meckel’s cartilage. The path of the ramus mandibularis trigeminus nerve is lateral to the rictalis and stegalis, and mesial to the malaris.

Levator arcus palatini. The levator arcus palatini has a roughly parallelogram shape ( Fig. 16 ), originating from the ventral margin of the frontal and sphenotic and inserting onto the hyomandibula. The origin of the levator arcus palatini is wider than its insertion, approximately one and a half of its insertion. At the insertion, the anterolateral and posterolateral fiber bundles of the levator arcus palatini are lateral to the malaris, while its anteromesial and posteromesial bundles are medial to the malaris. Only the dorsalmost fibers of the posterior portion of the levator arcus palatini are mesial to the dilatator operculi, but without reaching the median portion of the levator arcus palatini.

Figures

FIGURE 4 | Mesial view of adductor mandibulae of Hypopomus artedi (Hypopomidae), USNM 408442, 202. 7 mm LEA. Anatomical abbreviations in Tab. 1. Scale bar = 4 mm.

FIGURE 16 | Lateral view of dorsolateral musculature of Hypopomus artedi (Hypopomidae), USNM 408442, 202. 7 mm LEA. A= anterolateral fibers of the levator arcus palatini; P= posterolateral fibers of the levator arcus palatini. Remaining anatomical abbreviations in Tab. 1. Scale bar = 5 mm.