Microsternarchus Fernández-Yépez, 1968

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 : 34

Microsternarchus Fernández-Yépez, 1968

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. Its mesialmost fibers converge 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.

The rictalis originates in the preopercle, quadrate and hyomandibula. The lateralmost fibers of rictalis surpass the anterior margin of the preopercular fossa and reach the mid-portion of the preopercle. That subsection inserts mainly on the coronoid process, but with some lateral fibers on the anguloarticular and buccopalatal membrane. The stegalis arises from the hyomandibula, sphenotic, pterosphenoid, parasphenoid, sympletic and metapterygoid. Anteriorly, the stegalis differentiates into an intersegmental aponeurosis, dorsally entering the mandibular tendon and ventrally the meckelian tendon, inserting onto the coronomeckelian bone. 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 contacts it by slightly more than a half of the cartilage’s extension. The path of the ramus mandibularis trigeminus nerve is mesial to all sections of the adductor mandibulae, segmentum facialis.

Levator arcus palatini. The levator arcus palatini has a roughly parallelogram shape, 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 ( Fig. 19 ). At the insertion, the anterolateral, posterolateral and anteromesial fiber bundles of the levator arcus palatini are lateral to the malaris, while its posteromesial bundles are medial to the malaris. The posterodorsal fibers of the levator arcus palatini are parallel to the dilatator operculi, with no overlap between the two muscles. The truncus hyomandibularis nerve run through the lateral and mesial bundle of fibers of the levator arcus palatini.

Figures

FIGURE 19 | Lateral view of adductor mandibulae, pars malaris of Rhabdolichops eastwardi (Sternopygidae), MZUSP 81178, 188.3 mm LEA. Anatomical abbreviations in Tab. 1. Scale bar = 5 mm.