Hypopygus Hoedeman, 1962

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 : 38-39

Hypopygus Hoedeman, 1962

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 fibrous attachment, with its mesialmost fibers converging onto a small endomaxillary ligament less than one-third the length of the malaris. The latter inserts on the posteromedial portion of the maxilla.

The rictalis originates in the preopercle, quadrate and hyomandibula. The lateralmost fibers of the ventral portion of the rictalis surpass the anterior margin of the preopercular fossa and reach the mid-portion of the preopercle while posterodorsal fibers just fall short of the posterior portion of the same bone ( Fig. 11 ); and with its insertion occurring solely on the coronoid process. The stegalis arises from the hyomandibula, sphenotic, pterosphenoid, parasphenoid, sympletic and metapterygoid. Anteriorly, the stegalis differentiates into a poorly differentiated intersegmental aponeurosis, dorsally entering the mandibular tendon and ventrally the meckelian tendon, inserting onto the coronomeckelian bone. Towards the insertion, some lateral fibers are associated with the buccopalatal membrane, which is poorly differentiated from surrounding connective tissues. The stegalis is located laterally in relation to the proximal region of the endopterygoid and the adductor arcus palatini, overlaps those structures completely.

The segmentum mandibularis is located dorsally to coronomeckelian bone, with minimum (n = 3) or no (n = 1) contact with Meckel’s cartilage, extending for ca. 20% of the dorsal portion of that cartilage. 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 conical shape, originating from the ventral margin of the frontal and sphenotic and inserting onto the hyomandibula. The origin of the levator arcus palatini is approximately half as wide as its insertion ( Fig. 11 ). At 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 11 | Lateral view of dorsolateral musculature of Hypopygus lepturus (Hypopomidae), MZUSP 91426, 55.4 mm LEA. Some fibers of the LO, anterior accidentally removed during dissections. Anatomical abbreviations in Tab. 1. Scale bar = 2 mm.