A new catfish species of <scp> <i>Microcambeva</i> </scp> Costa &amp; Bockmann, 1994 ( <scp>S</scp> iluriformes: <scp>T</scp> richomycteridae) from southern Brazil, with a redescription of <scp> <i>M. ribeirae</i> </scp> Costa, Lima &amp; Bizerril, 2004

Among the few species of Microcambeva reported as occurring in more than one hydrographic basin, M. ribeirae has been previously listed from both the Ribeira de Iguape and the Guaraqueçaba basins. However, morphological and molecular analyses revealed that the specimens from Guaraqueçaba represent a new species, which is described in this study. Therefore, the distribution of M. ribeirae is restricted to the Ribeira de Iguape basin, and this taxon is redescribed. The new species is the southernmost record of the genus and is diagnosed among congeners by the T-shaped dark blotch in the dorsal portion of the head in preserved specimens. It is distinguished from most congeners, except for M. bendego and M. ribeirae, by the lack of a filamentous first pectoral-fin ray. Distinguished from the latter species by having only five pre-caudal vertebrae, the tip of the hyomandibula reaching the vertical through the anterior tip of the preopercle, and the last anal-fin ray branched. Molecular analysis of the cytochrome c oxidase subunit I (cox1) mitochondrial gene including most species of Microcambeva (except M. draco) supports the close relationship of the new species with M. ribeirae. The two species are nonetheless genetically different, with a 2.2% molecular distance. The conservation status and biogeography of the new species and of M. ribeirae are discussed.