Characidium mirim is described from the rio das Mortes, rio Araguaia basin in Central Brazil. The new species is distinguished from its congeners by having an incomplete lateral line, a conspicuous dark longitudinal stripe and dark transverse bars not extending ventrally to the lateral line, and by lacking the adipose fin and the dark caudal blotch. A phylogenetic hypothesis based on the available data on the phylogenetic relationships of the subfamily Characidiinae is presented. Results suggest that the new species is closely related to C.

Characidium nana is described from the Rio Xingu and Rio Tapajós drainages. The new species is distinguished from all its congeners by the absence of the inner series of dentary teeth, the absence of the parietal branch of the supraorbital laterosensory canal, the incomplete lateral line, the lack of an adipose fin, the presence of a conspicuous dark blotch on caudal peduncle as well as an evident dark, midlateral stripe, and the presence of 12 circumpeduncular scales. The relationships of the new species and its inclusion among the species of clade C4 are discussed.

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Two new species of Moenkhausia, one from the rio Tapajós and the other from the rio Xingu basins are described as apparently endemics of the Serra do Cachimbo. Both species, along with M. petymbuaba, share a distinct color pattern composed of large conspicuous dark blotches on the base of the body scales. Moenkhausia chlorophthalma, from rio Treze de Maio, a tributary to rio Curuá (rio Xingu basin), is distinguished by the presence of a proximal well delimited black area on the adipose fin and a green eye in life. Moenkhausia plumbea of the headwaters of tributaries of the rio Braço Norte, rio Tapajós basin is diagnosed by the presence of a dark longitudinal stripe across the eye and six branched pelvic-fin rays (vs. seven). Relationships of the new species with other Moenkhausia are discussed.Duas espécies novas de Moenkhausia, uma da bacia do rio Tapajós e outra da bacia do rio Xingu, são descritas como aparentemente endêmicas da Serra do Cachimbo. Ambas, juntamente com M. petymbuaba, compartilham um padrão de colorido exclusivo de grandes manchas escuras conspícuas na base das escamas do corpo. Moenkhausia chlorophthalma, do rio Treze de Maio, um afluente do rio Curuá (bacia do rio Xingu), é facilmente reconhecida pela presença de uma área preta bem delimitada na região anterior da nadadeira adiposa e possuir olhos verdes em vida. Moenkhausia plumbea ocorre nas cabeceiras dos afluentes do rio Braço Norte, bacia do rio Tapajós, e pode ser diagnosticada pela presença de uma faixa longitudinal escura no olho e seis raios ramificados na nadadeira pélvica (vs. sete). As relações entre as novas espécies com as demais Moenkhausia são discutidas.

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Erythrocharax altipinnis is described from the Serra do Cachimbo, Pará, Brazil. The new taxon is distinguished from all of the Characidae genera by having the pelvic bones firmly attached through the isquiatic processes; a nearly triangular hiatus in the musculature covering the anterior chamber of the swim bladder between the first and second pleural ribs (pseudotympanum); the pedunculate, notably expanded and distally compressed teeth in both jaws; circumorbital series represented by antorbital and four infraorbital bones with laterosensory canals not enclosed; a single tooth row in the premaxillary with the teeth perfectly aligned and similar in shape and cusp number; the first three branched dorsal-fin rays distinctly elongate in males; a bright red adipose and caudal fins in life; a conspicuous dark midlateral stripe extending from the opercle to the tip of the median caudal-fin rays; and by the absence of a humeral spot. The phylogenetic position of the new taxon is discussed using morphological and molecular datasets, with conflicting results of both approaches discussed. Additionally, a summarized discussion on the current problems in the Characidae taxonomy is presented and the principal biases in the morphological dataset are also discussed.

Lebiasina yepezi, a new Lebiasininae with a conspicuous color pattern, is described. The new species is endemic of the headwaters of the rio Negro, rio Branco, and rio Orinoco in the Serra Parima-Tapirapecó Mountains, at the border of Brazil and Venezuela. The new species is readily distinguished from all other Lebiasininae by the presence of four black longitudinal stripes on the trunk, and the triangular shaped dorsal surface of the mesethmoid, lacking lateral projections. The unusual color pattern is contrasted with those of other lebiasinin, as well as members of the pyrrhulinin genus Nannostomus. A close relationship between Lebiasina yepezi and the Gran Sabana (Venezuela) species is suggested based in color pattern features. The present contribution corresponds to a further refutation of the type locality of L. intermedia, as suggested on its description, since Lebiasinins, except L. bimaculata, L. boruca, and L. festae, do not occur in low land waters.Lebiasina yepezi, um novo Lebiasininae com um conspícuo padrão de colorido, é descrito. A nova espécie é endêmica das cabeceiras do rio Negro, rio Branco e rio Orinoco, na Serra Parima-Tapirapecó, ao longo da fronteira entre Brasil e Venezuela. A nova espécie é prontamente diferenciada das demais espécies pela presença de quatro faixas longitudinais escuras ao longo do corpo, e a superfície dorsal do mesetmoide com o formato triangular, não apresentando projeções laterais. O padrão de colorido incomum é comparado com o dos demais Lebiasininae e também com o dos Pyrrhulininae do gênero Nannostomus. Uma próxima relação é proposta entre Lebiasina yepezi e as espécies da Gran Sabana (Venezuela) com base em caracteres de colorido. A presente contribuição corresponde a mais uma refutação da localidade-tipo de L. intermedia conforme sugerida na descrição daquela espécie, uma vez que os lebiasiníneos, com exceção de L. bimaculata, L. boruca e L. festae, não ocorrem em rios de terras baixas.

Pyrrhulina marilynae, new species, is described. The new species can be distinguished among congeners mainly by presenting a conspicuous, dark, zigzag shaped primary stripe, extending to distal end of median caudal-fin rays, reduction of the number of precaudal vertebrae, absence of postcleithrum 2, and nine principal rays on caudal-fin dorsal lobe. The putative relationship of the new species with Pyrrhulina australis, P. vittata and P. zigzag, three small-sized species of the genus, is discussed.