Trichomycterus comprises about 170 valid species, but its monophyly has been challenged in the last decades. Bayesian Inference and Maximum Likelihood analyses comprehending mitochondrial genes COI and CYTB and nuclear genes GLYT, MYH6 and RAG2 from 71 Trichomycterinae terminal taxa and eight outgroups were performed. The analyses highly supports a clade containing Trichomycterusnigricans, the type species of the genus, and several other congeners endemic to eastern and northeastern Brazil, herein considered as the genus Trichomycterus, the sister clade the southern Brazil and adjacent areas clade; the latter clade comprises two subclades, one comprising species of the genus Scleronema and another comprising species previously placed in Trichomycterus, herein described as a new genus. Cambevagen. n. is distinguished from all other trichomycterines by the presence of a bony flap on the channel of the maxillo-dentary ligament, the interopercle shorter than the opercle, a deep constriction on the basal portion of the antero-dorsal arm of the quadrate, absence of teeth in the coronoid process of the dentary, the maxilla shorter than the premaxilla, the cranial fontanel extending from the the medial posterior of frontal to the medial region of supraoccipital, and absence of the postorbital process of the sphenotic-prootic-pterosphenoid.

This study is primarily directed to the most poorly known species of the genus Trichomycterus, comprising five nominal species (T. florensis, T. immaculatus, T. nigricans, T. paquequerensis and T. santaeritae) endemic to south-eastern Brazil. One of them, T. nigricans, is the type species of the genus, involved in taxonomic problems for over 150 years. A detailed historical review, accompanied by examination of type specimens and recent collections, revealed that the correct type locality of T. nigricans is in the vicinity of Rio de Janeiro, not Santa Catarina as commonly appears in the literature; specimens previously misidentified as T. nigricans from Santa Catarina belong to a possibly undescribed species of the genus Cambeva; T. paquequerensis is a synonym of T. immaculatus, and T. florensis is a synonym of T. santaeritae; and the hypothesis that T. santaeritae is closely related to the Amazon Sarcoglanidinae is refuted. The three valid species are redescribed. These species are members of a clade also including T. caipora that is highly supported by molecular data, diagnosed by a pronounced posterior maxillary process and caudal fin emarginate at least in larger specimens. A subclade comprising T. caipora, T. nigricans and T. santaeritae is diagnosed by a long maxilla and a bifid anterior extremity of hypobranchial 3.

The mountain area between the Mantiqueira and Espinhaço ranges of south-eastern Brazil is of special interest for biologists by sheltering headwaters of two of the largest South American river basins, as well as comprising sections of two main world biodiversity hotspots. Mineral exploitation activities have caused great environmental impact, but biological inventories have demonstrated a rich biota with some organisms still poorly known. We herein analyse catfishes of the Trichomycterus reinhardti species group, endemic to this area. With the objective of inferring species limits, we combine morphological variation to unilocus coalescent methods of species delimitation using fragments of the mitochondrial genome (total of 1924 bp) for 38 individuals collected in 14 sites. The phylogenetic analysis supported a clade endemic to the Rio São Francisco basin and neighbouring Rio Doce headwaters, Espinhaço mountain range, and another one, endemic to the Rio Grande drainage, Rio Paraná basin, between Mantiqueira and Canastra mountain ranges. This biogeographic pattern may be explained by geological evidence indicating that the upper Rio Grande drainage was connected to the upper Rio São Francisco basin until the Middle Miocene, instead of being part of the Rio Paraná basin as today. The integrative analysis supported a total of 10 species, six of which are new and here described. Interestingly, the small areas inhabited by species here delimited are highly coincident with the distribution range of other mountain fish species. High level of local species endemism is possibly related to the uncommon regional relief, with small subdrainages crossed by transversal hills as a result of geological gaps, supporting a complex palaeogeographic scenario favouring isolation of taxa in small areas. Under a conservation perspective, these small areas of endemism for mountain fishes deserve special attention due to the process of environmental decline along centuries in the region. http://www.zoobank.org/urn:lsid:zoobank.org:pub:0E3981E9-D7A9-4C9B-B56A-85621F33A7CB