A new subfamily, Delturinae, is described to accommodate the loricariid catfish genera Delturus Egenmann & Eigenmann, 1889 and Hemipsilichthys Eigenmann & Eigenmann, 1889, a clade recently demonstrated to be the sister group of all remaining loricariids except Lithogenes. The genus Hemipsilichthys is restricted to three species, H. gobio (Lütken, 1874), its sister species H. papillatus Pereira et al., 2000, and H. nimius Pereira et al., 2003. Relationships among species of Delturus were not resolved and a new species, D. brevis, is described from the Rio Jequitinhonha basin in eastern Brazil. The geographical distribution of Delturinae, exclusively on the south‐eastern Brazilian Shield, indicates that south‐eastern Brazil acts as either a refugium for basal loricariid taxa or a point of origin for the Loricariidae. Lectotypes are designated for D. parahybae Eigenmann & Eigenmann, 1889 and Plecostomus angulicauda Steindachner, 1877. Keys are presented for subfamilies of Loricariidae and for genera and species of Delturinae. Diagnoses are provided for all delturine clades and species. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 147, 277–299.

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A phylogenetic study of the Loricariidae with emphasis on the Neoplecostominae is presented based on a maximum parsimony analysis of 268 phenotypic characters encompassing osteology, arthrology, and external morphology. Results support previous hypotheses of the monophyly of the Neoplecostominae and each of the included genera: Hirtella, Isbrueckerichthys, Kronichthys, Neoplecostomus, Pareiorhaphis, and Pareiorhina. In addition, previously undiscovered diversity was revealed within the subfamily as an additional genus-level taxon, herein described as Euryochus. Relationships among neoplecostomine genera are: (Kronichthys (Euryochus ((Hirtella + Pareiorhaphis) (Pareiorhina (Isbrueckerichthys + Neoplecostomus))))). Additional undescribed diversity was also detected among most neoplecostomine genera and the Hypoptopomatinae. In addition, recently discovered genera Nannoplecostomus and Microplecostomus were included in the analysis, and were identified as sequential sister-taxa to Neoplecostominae + Hypoptopomatinae, which are currently not included in any subfamily and regarded as incertae sedis in Loricariidae. The three species of Lithogenes were included in an encompassing phylogenetic analysis for the first time, and were identified as a monophyletic unit and sister group to all remaining loricariids. The other loricariid subfamilies were also corroborated as monophyletic, and presented the following interrelationships (Lithogeninae (Delturinae (Loricariinae (Hypostominae (Nannoplecostomus (Microplecostomus (Hypoptopomatinae + Neoplecostominae). The Neoplecostominae and its genera are phylogenetically diagnosed, and hypothesized relationships are compared to those of previous morphological and molecular phylogenetic studies.

A new species of the loricariid subfamily Neoplecostominae is described on the basis of specimens obtained from the headwaters of the rio Iguaçu basin in the State of Paraná, southern Brazil. Pareiorhaphis parmula is the first representative of the genus discovered from the rio Paraná basin and expands the geographic distribution of the genus. It is diagnosed from other Pareiorhaphis species by having one small plate on each side of the pectoral girdle, just posterior to the gill opening and the club-shaped pectoral-fin spine, broadening from base to tip in adult males. All species formerly included in Hemipsilichthys except H. gobio, H. papillatus, and H. nimius are transferred to the genus Pareiorhaphis, which is resurrected from the synonymy of Hemipsilichthys.
Uma nova espécie de loricarídeo pertencente a subfamília Neoplecostominae é descrita com base em espécimes obtidos das cabeceiras do rio Iguaçu, estado do Paraná, sul do Brasil. Pareiorhaphis parmula é a primeira espécie do gênero descrita para a bacia do rio Paraná expandindo a distribuição do gênero. Se diferencia das demais espécies do gênero pela presença de uma única e pequena placa na região ventral posterior a abertura branquial e pelo formato de clava do raio indiviso da nadadeira peitoral, estreito na base e alargando-se em direção à extremidade do raio em machos adultos. Todas as espécies previamente incluídas em Hemipsilichthys com exceção de H. gobio, H. papillatus e H. nimius são transferidas para o gênero Pareiorhaphis, que é retirado da sinonímia de Hemipsilichthys