Moenkhausia petymbuaba, new species, is described from the upper Rio Curua, a tributary of the Rio Iriri, middle Rio Xingu basin, in the Serra do Cachimbo plateau, Para state, Brazil. The new species is easily distinguished from its congeners by the presence of a broad, well-defined dark longitudinal stripe and series of longitudinal dark blotches along the dorsal and lateral surfaces of body, which are more developed above the dark longitudinal stripe.

Jupiaba poekotero, new species, is described from the Rio Tiquie, a tributary of the Rio Uaupes, in the upper Rio Negro system, estado do Amazonas, Brazil. It is distinguished from its congeners by the presence of an unpigmented, horizontally-oriented, roughly oval area on the proximal portion of the caudal-fin lobes, bordered posteriorly by dark pigmentation. Comments on the putative relationships of the new species are provided.

A new Knodus is described from the rio do Peixe, a tributary of the rio Cabw al, in the upper portions of the rio Paraguay basin in Mato Grosso state, Brazil. It can be distinguished from its congeners, and in fact from all remaining characid fishes, by the presence of two symmetric, large dark blotches basally on caudal fin lobes. Comments on the disputed recognition of the genus Knodus are provided.

Aspidoras velites, from the upper Rio Araguaia basin (Rio Tocantins drainage) in Central Brazil, is described. The new taxon is an unusual corydoradine species, showing several reductive features, and resembling in external morphology and coloration the loricariid hypoptopomatine catfishes. The new species differs from its congeners by a naked predorsal area, the first pectoral-fin element not modified as a spine, a weak dorsal spine, minute vermiculate platelets on the ventral surface between the isthmus and pelvic regions, a short narrow posterior process of supraoccipital, and the presence of three longitudinal dark stripes. Some of the features presented above are reductive, possibly indicating that the new species is paedomorphic.

A new Moenkhausia species is described from the middle rio Negro of Brazil. This species shares with Moenkhausia oligolepis, Moenkhausia sanctaefilomenae, and Moenkhausia pyrophthalma a reticulate body coloration and a red pigmentation on the dorsal margin of the eye. It can be distinguished from those species by the presence of a distinctive stripe on the caudal peduncle, a uniform anterior humeral blotch, and meristic and morphometric data. Priocharax ariel, Serrabrycon magoi, Microsternarchus fimbripinnus, and Acestridium martini are recorded for the first time from the middle rio Negro in Brazil.

A new species of Aspidoras is described from the tipper rio Itiquira and the tipper rio Taquari, rio Paraguai basin, and represents the first record of the genus from this river system. The new species differs front its congeners by the following unique features: infraorbitals and preopercle covered by skin; nuchal plate reduced and covered by skin; and lateral line absent from body plates posterior to the two small lateral line ossicles. The new species exhibits the greatest body size observed for an Aspidoras species. The occurence of Aspidoras in tributaries of the rio Paraguai basin extends the range of the genus further southwest than previously known, encompassing most of the river basins that drain the Brazilian Shield.