A taxonomic review of the waspfish genus Matsubara 1943 (Tetrarogidae), diagnosed by the following combination of characters: body sparsely covered with small embedded cycloid scales, palatine teeth present, XIII-XVI dorsal-fin spines, the first dorsal fin originating above the orbit, five pelvic-fin soft rays, and membrane of lower four pectoral-fin rays deeply incised, resulted in the recognition of six species: (Weber 1913), (Lloyd 1909a), Matsubara 1943, Klausewitz 1985, (Smith 1958), and Chan 1966. (anti-tropically distributed in East Asia and Australia) can be distinguished from its congeners by the presence of three dark blotches on the body (vs. absent or a single blotch); (eastern Indian Ocean) and (Philippines to Australia) differ from other congeners in having a black blotch behind the opercle (vs. blotch absent), with the former distinguishable from the latter by dorsal rows of dark spots on the body, and pectoral and caudal fins (vs. spots absent), and 79-96 scale rows in the longitudinal series (vs. 94-137); (Red Sea) differs from (southwestern Indian Ocean) and (northwestern Pacific Ocean) in having the lowermost four pectoral-fin rays elongated and XIII (vs. XIV-XVI) dorsal-fin spines, the latter species being separated by the symphyseal knob condition (unremarkable, vs. pronounced, ), dark dorsal spots on the body (vs. absent), and 5 anal-fin soft rays (vs. 6 or 7). Keys to the genera of Tetrarogidae and species of are given, including taxonomic status of Jordan and Richardson 1910 and Mandrytsa 2001.

Cichlid fishes are an important model system in evolutionary biology, primarily because of their exceptional diversity. However, while some cichlid assemblages, such as the ones of the African Great Lakes, have received considerable attention, others are not well studied, including many riverine species. Here, we focus on the species group and first report a new record of in the upper Paranaíba River drainage, extending the known distribution range of this genus. Through Bayesian inference and maximum likelihood phylogenetic analyses of the mitochondrial cytochrome gene of these specimens as well as available sequences, we assigned the newly discovered population to . We corroborate the monophyly of the species group and the presence of three species in the upper/middle Paraíba do Sul River basin as well as molecular diagnostic characters for each. Finally, we provide evidence for a recent expansion of .