Untangling the threads: phylogenetic relationships of threadfins (Percomorphacea: Perciformes: Polynemidae)

Threadfins are primarily marine bony fishes that have part of the pectoral fin modified into specialized sensitive filaments. They compose the Polynemidae, a family with eight genera and 42 extant species. The internal relationships and phylogenetic position of Polynemidae within Percomorphacea are controversial, with highly conflicting hypotheses proposed by both molecular and phenotypic analyses. We performed a cladistic analysis of threadfins based on the most comprehensive sampling of morphological data ever done. The final dataset included 197 characters from external morphology, the laterosensory system, osteology, myology and neurology in representatives of all valid polynemid genera. More than half of the characters are reported here for the first time, notably the myological ones. A sensitivity analysis of 11 different weighting schemes (equal weighting and extended implied weighting parsimony) resulted in a fully resolved tree. Sciaenidae, not Pleuronectiformes, is recovered as sister to Polynemidae. All polynemid genera are resolved as monophyletic except Polydactylus, which is polyphyletic. Filimanus, Pentanemus and Polydactylus s.s. appear as successive sister taxa of all remaining threadfins. Leptomelanosoma, Parapolynemus and Polynemus form a monophyletic group. Eleutheronema and Galeoides appear intercalated with other species of Polydactylus in the apical portions of the polynemid tree.