Hypergastromyzon revisited, with descriptions of a new genus and two new species (Teleostei: Gastromyzontidae)

The genus Hypergastromyzon is revised based on fresh topotypic specimens and two other locations in Borneo. Hypergastromyzon humilis is redescribed, along with descriptions of H. abditus, new species, from upper Katingan basin; and H. sambas, new species, from upper Sambas basin. A new genus, Engkaria, is erected to accommodate H. eubranchus. Engkaria differs from Hypergastromyzon in having very distinct sexual characters where males have heavy tuberculation over the opercle and modified pectoral-fin rays, the pelvic fins are not completely fused, and other characters. Engkaria eubranchus is redescribed based on a series of fresh specimens. An artificial key is provided for all species of Hypergastromyzon.