A new species of Anchoviella (Clupeiformes: Engraulidae) from the western Amazon River in Peru, with comments on congeners in the Peruvian Amazon River.

Anchoviella hernanni sp. nov. is described from the upper Amazon River basin, in tributaries of the Marañon, Ucayali and Madre de Dios river drainages that drain the Peruvian Andes. The new taxon can be distinguished from all congeners except Anchoviella jamesi, Anchoviella manamensis and Anchoviella perezi, by having 12-15 gill rakers in the lower branch of the first gill arch (v·16-35) and from those species by the distance between verticals through the posterior margin of the orbit to the posterior margin of the upper jaw 9·5-14·8% head length; LH (v. up to 6·0% LH ). An updated identification key of all freshwater species of Anchoviella and morphological comparisons between all species of the genus occurring in Peru are provided.

Redescription of Hysteronotus megalostomus (Characiformes: Characidae: Stevardiinae), a poorly known characid from tributaries of the Rio São Fancisco, Brazil with comments on the conservation of the species.

Originally described from the upper Rio das Velhas, a tributary of the Rio São Francisco, state of Minas Gerais, Brazil, Hysteronotus megalostomus was recently collected in many tributaries of the Rio São Francisco north of the type locality. The specimens of the population samples collected outside the type locality share the morphological features present in the type material except for the presence of an adipose fin found only in two specimens within the more recently collected material. Presence or absence of the adipose fin has been extensively used by fish taxonomists to characterize different species and even genera, but in H. megalostomus the character is not consistent, indicating its use alone is not diagnostic. The species is redescribed and its phylogenetic relationships and conservation status are briefly discussed.

A new species of Rhinopetitia Géry 1964 (Ostariophysi: Characiformes: Characidae) from the Rio Teles Pires, Rio Tapajós basin, Brazil.

A new species of Rhinopetitia is described from the Rio Teles Pires, a major tributary of the Rio Tapajós. The new taxon is distinguished from its only congener, Rhinopetitia myersi, by having all premaxillary teeth in both rows with seven to nine cusps, maxillary teeth with seven or eight cusps, a distinct dark midlateral stripe on the body and a round humeral blotch (v. outer series of premaxillary teeth with three cusps and inner series of premaxillary teeth with three to five cusps, maxillary teeth with three to five cusps, the absence of a dark midlateral stripe and humeral blotch). Putative characters suggesting a close relationship between Rhinopetitia, Bryconacidnus, Ceratobranchia, Monotocheirodon, Odontostoechus, Othonocheirodus and Rhinobrycon are presented. This putative clade is included in the Stevardiinae, a monophyletic group within the Characidae.