Three new species of freshwater halfbeaks (Teleostei: Zenarchopteridae: Hemirhamphodon) from Borneo

Abstract

Three new species of Hemirhamphodon are described from Borneo island. Hemirhamphodon sesamum, new species, from lowland basins draining into the Makassar Strait, differs from its congeners in having unique colour markings on its dorsal fin and lower jaw; males with posterior projections on the fourth anal-fin ray, with third, fourth and eighth anal-fin rays branched, and with posterior projections on the fourth anal ray; females with third and fourth anal-fin rays branched. Hemirhamphodon byssus, new species, from southern Sarawak differs from the allopatric H. kuekenthali in having the anterior dorsal-fin ray extensions reaching to the middle of the caudal fin (vs absence or small extensions on dorsal-fin rays), black pigment on the anterior half of dorsal fin (vs middle part of dorsal fin), males with posterior projections on the fourth anal-fin ray. Hemirhamphodon kecil, new species, from the lower Mahakam in East Kalimantan, can be distinguished from its congeners in having few or no markings except for sparse black pigment along sub-margin of the dorsal fin and anterior dorsal margin of the caudal-fin base. It is a small species (up to 41 mm SL). Notes and a figure of the holotype of H. phaiosoma are provided, along with colour descriptions of fresh material. An artificial key to Hemirhamphodon, inclusive of the new species, is also included. © National University of Singapore.