The Rio Grande drainage plays a key role in supplying water and electricity to large urban centres, but some components of its rich ichthyofauna are still poorly known. Based on our field inventories in the middle section of the drainage, we recognised 10 trichomycterine endemic species, of which 6 species are new and described herein. A molecular analysis (2600 bp for 43 taxa) indicated that the species of both subgenera do not form monophyletic groups. One species of the subgenus Cryptocambeva is closely related to species from the inner Brazilian Plateau, whereas other species of this subgenus are closely related to species endemic to smaller coastal basins. The species of the subgenus Paracambeva belong to different lineages of a clade endemic to the Rio Grande drainage. These species are diagnosed by the characters of their external morphology and osteology. A key to species identification is provided. The species distribution patterns support delimitation of three areas of endemism, which may have a relevant role for proposals of conservation strategies: the Uberaba, the São João-Sapucaí, and the Tamborete areas. The last one, a small area confined between the Serra da Canastra and the Rio Grande at the Furnas dam, is particularly important for sheltering three endemic trichomycterines and two loricariid catfishes.

Psammocambeva, a subgenus of Trichomycterus s.s., includes a clade endemic to south-eastern Brazil, the Psammocambeva alpha-clade (PAC), containing species with similar colour pattern and fin morphology, making difficult their identification without accurate examination. The greatest diversity of PAC species occurs in the Rio Paraíba do Sul basin area (RPSA), situated within the Atlantic Forest, one of the most important and endangered biodiversity centres in the world. Herein, we: perform a multigene phylogeny focusing on species of PAC; revise morphological characters diagnosing species of PAC from the RPSA, with special attention to those equivocally synonymised in a recent study; describe two new species, and provide a key for species identification. Molecular and morphological evidence supported the recognition of eight valid species belonging to four species complexes. Data indicated that T. auroguttatus, T. travassosi, and T. longibarbatus are valid species. Finally, we discuss the negative impacts of underestimating species diversity in regions under the intense process of natural habitat loss, concluding that integrative approaches are important tools to estimate species diversity, but they should include a range of morphological characters informative to delineate and diagnose groups and their respective species, in association with phylogenies generated by robust molecular datasets.

The Rio Doce basin is situated in a biodiversity hotspot, with some fish groups still superficially known. The intense process of habitat loss and water contamination justifies efforts to speed up the pace of describing fish species diversity. Herein, we focus on a clade of trichomycterine catfishes, subgenus Psammocambeva, genus Trichomycterus, performing a multigene phylogenetic analysis, which integrated to a comparative morphological analysis corroborates monophyly and relationships of four species complexes. Five new species are recognised and described. Species distribution patterns support the recognition of five areas of endemism for trichomycterines, most of which are well-known biodiversity centres: Serra do Espinhaço, Serra do Brigadeiro, Serra do Caparaó, Serra do Castelo, and upper-middle Rio Doce. Trichomycterine diversity in the Rio Doce basin, with 16 species, of which 15 belong to Psammocambeva, is lower than in the smaller neighbouring Rio Paraíba do Sul basin, with 21 species in five subgenera. Data suggest that species diversification in the former basin is relatively younger, following the initial diversification of Psammocambeva in the Miocene, whereas diversification in the latter basin has been estimated to have occurred during the Oligocene. This study reinforces the importance of naming new taxa and delimitating areas of endemism as primary tools for conservation strategies.