Taxonomic review of the genus Trichomycterus Valenciennes (Siluriformes: Trichomycteridae) from the laguna dos Patos system, Southern Brazil

The species of the genus Trichomycterus inhabiting the laguna dos Patos system are reviewed and five species are recognized. Trichomycterus tropeiro Ferrer & Malabarba has a restricted range and is endemic to the uppermost portion of the rio das Antas. Trichomycterus balios, n. sp., is distributed in the upper portion of the rio das Antas and rio Cai basins. Trichomycterus diatropoporos, n. sp., is endemic to the rio da Prata basin, a tributary of the rio das Antas. Trichomycterus poikilos, n. sp., is widely distributed in the upper portion of the rio Jacui basin and tributaries of the rio Taquari-Antas. Trichomycterus brachykechenos, n. sp., is endemic to the upper portion of the rio dos Sinos. The new species are distinguishable from most congeners, except for T. davisi, T. mboycy, T. naipi, T. payaya, T. papilliferus, T. perkos, T. plumbeus, and T. tropeiro by the lower number of pectoral-fin rays (I+5-6) and by the first pectoral-fin ray not prolonged as a filament. Other characters distinguish the new taxa from these eight species. The distribution of the genus in the laguna dos Patos system is discussed and a taxonomic key is provided.