Redescription of a rare threadfin (Perciformes: Polynemidae), Polydactylus macrophthalmus (Bleeker, 1858), with designation of a lectotype and notes on distributional implications

A rare threadfin, Polydactylus macrophthalmus (Bleeker, 1858), having long been included in the genus Polynemus, is redescribed on the basis of 9 specimens and a lectotype designated. Polydactylus macrophthalmus is characterized by the following combination of characters: 7 pectoral filaments, upper 3 filaments extending beyond posterior margin of hypural; 13 or 14 pectoral fin rays; 87–94 pored lateral line scales; 11 scales above lateral line, 15 or 16 below; 10–12 upper series gill rakers, 15 or 16 lower, 26 or 27 total; occipital profile concave in adults; second spine of first dorsal fin very strong; pectoral fin rays long (mean 24% [range 24–26%] of SL). The presently known distribution of the species, including the Kapuas River, Kalimantan, and the Musi and Batanghari Rivers, Sumatra, Indonesia, apparently reflects the ancient Central or North Sunda River during the last period of lowered sea levels, ca. 12 000 years ago