Brachyhypopomus, Mago-Leccia, 1994

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 : 31-32

Brachyhypopomus Mago-leccia, 1994

Adductor mandibulae. The malaris arises from the mid-dorsal portion of the hyomandibula and inserts 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 ( Fig. 13 ). Except for B. sullivani and B. regani , the malaris has a concavity on its dorsal margin for accommodating the eyeball.

The rictalis originates in the preopercle, quadrate and hyomandibula, or only in the preopercle and hyomandibula in B. pinnicaudatus , B. hendersoni and B. regani . The lateralmost fibers of rictalis surpass the anterior margin of the preopercular fossa and reach the mid-portion of the preopercle in most species of Brachypopomus analyzed herein. It reaches the posterior margin of that bone in B. bombilla , B. pinnicaudatus , and B. hendersoni . That section inserts mainly on the coronoid process, but with some lateral fibers on the anguloarticular in B. bombilla , B. sullivani , and B. gaudeiro . 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, overlapping it completely; except in B. pinnicaudatus , in which the stegalis overlaps only the posterior portion of the basal region of the bone. Normally, the stegalis is positioned laterally to the adductor arcus palatini, overlapping it completely, except in B. pinnicaudatus , B. brevirostris , B. hendersoni , and B. regani , where the stegalis overlaps only the mid-posterior portion of the adductor arcus palatini.

Commonly, the segmentum mandibularis is located dorsally to Meckel’s cartilage and contacts it, except in B. sullivani , B. beebei , B. gaudeiro , and B. draco , where the segmentum mandibularis is restricted to the dorsal margin of the coronomeckelian bone, and does not contact the dorsal margin of Meckel’s cartilage. The path of the ramus mandibularis trigeminus nerve is invariably mesial to the malaris and rictalis, and lateral to the stegalis.

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 slightly wider than its insertion; or equal in B. draco and B. hendersoni . 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. In most examined species, the levator arcus palatini is parallel to the dilatator operculi, with no overlap. In B.

regani only, the posterodorsal fibers of the levator arcus palatini are mesial to the dilatator operculi, but without reaching the median portion of the levator arcus palatini.

Figures

FIGURE 13 | Adductor mandibulae, pars malaris of Brachyhypopomus janeiroensis (Hypopomidae), MZUSP 22702, 80.9 mm LEA. A. Lateral view; B. Mesial view. Buccopalatal membrane dissected ventrally. Anatomical abbreviations in Tab. 1. Scale bars = 1 mm.