The Polynemidae is a family of primarily marine fishes with eight genera and 42 extant species. Many aspects of their morphology are largely unknown, with few reports about their osteology and barely any information on their myology. This paper describes and illustrates in detail all facial and branchial muscles of representative species of polynemids. Our analysis demonstrates the existence of several remarkable and previously unknown specializations in the polynemid musculature. The aponeurotic and completely independent origin of the pars promalaris of the adductor mandibulae is apparently unique among percomorphs. The differentiation of this section into lateral and medial subsections; the total separation of the promalaris from the retromalaris; the differentiation of the pars primordialis of the levator arcus palatini into external and internal subsections are also uncommon features of polynemids that are shared by sciaenids, thus supporting the hypothesis of a closer relationship between these families.
