ABSTRACT. The morphological discrimination between the speciesAstyanax altiparanae and A. asuncionensis of the upper Paraná River and Paraguay River basins, respectively, has always been difficult. Two D-loop haplogroups of A. altiparanae are known, one with the presence (AltoPR) or the absence (AltoPR-D) of a 32-bp block similar to that in A. asuncionensis. We examined these samples to characterize A. altiparanae

least 15 OTUs were determined, eight of which belonged to the carapo complex. Our results indicate the existence of at least four Gymnotus species belonging to the carapo clade in the upper Paraná River basin and possibly erroneous previous identifications. Besides that, we identified a possible new species of Gymnotus in the Rio Doce basin. The Generalized Mixed Yule Coalescent (GMYC) and Poisson Tree Processes (PTP) molecular delimitation approaches place other specimens found in the upper Paraná River and Guaíba River (Gymnotus sp.) in well-established groups that should be considered in studies involving the carapo complex. K E Y W O R D S

In a recent expedition to the rio Grande basin, a tributary of the rio Paraná in southern Brazil, individuals of the armoured catfish genus Hypostomus with a peculiar and beautiful colour pattern composed of pale vermiculations on the head and four to five horizontal stripes on the flanks were collected. Initially, the specimens were identified as a colour morph of the pale-spotted H. margaritifer. However, when we compared their partial cytochrome C oxidase subunit I (COI) mitochondrial gene to sequences of some typically pale-spotted H. margaritifer, the striped specimens were genetically distinct. Further analysis of the striped individuals revealed that they are the poorly known but valid species Hypostomus variipictus, which was described by Ihering in 1911 from the rio Pardo, a tributary of the rio Grande, upper rio Paraná basin, in São Paulo State, Brazil. Since its descriptions, no robust taxonomic work has been published concerning this species. In this study, the newly sampled population was compared to the original description and to the holotype of H. variipictus, providing the foundation for a complete redescription, proper diagnosis, and first live colour illustration and description of the previously hidden H. variipictus.