A new species of spiny Rineloricaria (Siluriformes: Loricariidae) from the Rio Paraba do Sul basin and costal rivers from Rio de Janeiro State.

Although the genus Rineloricaria is widely distributed in the Neotropical region, its species usually occupy single drainages with high habitat fidelity. Rineloricaria species show evident sexual dimorphism with hypertrophied odontodes in sexually mature males. Here, we describe a new species of Rineloricaria present in the Rio Paraiba do Sul basin and coastal rivers in Rio de Janeiro State. The new species has extreme sexual dimorphism making possible to differentiate it from all congeners. The new species can also be separated from other sympatric species by morphometric characteristics and dermal plates pattern.

New species of the Pseudancistrus barbatus group (Siluriformes, Loricariidae) with comments on its biogeography and dispersal routes.

A new species of Pseudancistrus is described from the Tapajós Basin, and assigned to the P. barbatus group by having hypertrophied odontodes along the snout and lacking evertible cheek plates. The new species is distinguished from other species in that group (P. barbatus, P. corantijniensis, P. depressus and P. nigrescens) by its pattern of spots, length and color of snout odontodes, greater head depth, cleithral width, anal-fin spine length, peduncle depth and internares width. Molecular phylogenetic results corroborate placement of the new species in the Pseudancistrus barbatus group which is otherwise distributed in the Xingu Basin and rivers draining the Guyana Shield into the Atlantic Ocean. Topology tests strongly reject alternative hypotheses supporting close relationships with Guyanancistrus, Lithoxancistrus or the species Pseudancistrus pectegenitor, P. sidereus and P. genisetiger. Additionally, we propose two hypotheses on the distribution of the new species in the rio Tapajós, a Brazilian Shield drainage. The first one proposes that ancestral stock of the P. barbatus group was widely distributed throughout rivers draining the Guyana and Brazilian shields, and the species P. zawadzkii and Pseudancistrus sp. L17 are in the limit of the distribution for the group in Tapajós and Xingu rivers. The second hypothesis proposes that ancestral stock of the P. barbatus group was restricted to Guyana Shield rivers, and that headwater capture events permitted several dispersal routs through Guyana and Amazon rivers, permitted that the ancestral lineages of Pseudancistrus sp. L17 and P. zawadzkii reached the rivers of Amazon basin.

Pareiorhina hyptiorhachis, a new catfish species from Rio Paraíba do Sul basin, southeastern Brazil (Siluriformes, Loricariidae).

Pareiorhina hyptiorhachis is described from Ribeirão Fernandes and Rio Pomba, Rio Paraíba do Sul basin, Brazil. The new species is distinguished from its congeners (Pareiorhina brachyrhyncha, Pareiorhina carrancas, Pareiorhina cepta, and Pareiorhina rudolphi) by the presence of a conspicuous ridge on the trunk posterior to the dorsal fin (postdorsal ridge), simple teeth, a completely naked abdomen, a round dorsal profile of the head, greater suborbital depth and greater head width. We discuss the distributional pattern of the new species and its congeners and hypothesize that headwater capture is responsible for the distribution of Pareiorhina species across different watersheds in southeastern of Brazil.

ResumoPareiorhina hyptiorhachis é descrita do ribeirão Fernandes e do rio Pomba, bacia do rio Paraíba do Sul, Brasil. A nova espécie é distinguida de suas congêneres (Pareiorhina brachyrhyncha, Pareiorhina carrancas, Pareiorhina cepta, e Pareiorhina rudolphi) por caracteres relacionados a presença de uma quilha conspícua na superficie pós-dorsal do tronco, dentes simples, abdomen completamente nú, perfil dorsal da cabeça arredondado, altura do sub-orbital e largura da cabeça. Nós discutido o padrão de distribuição da nova espécie e de seus congêneres e a hipótese de que a captura de cabeceira é responsável pela distribuição das espécies de Pareiorhina através das diferentes bacias hidrográficas do sudeste do Brasil.