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Oligosarcus itau n. sp. is described. This species is the sister group of the remaining analyzed species of Oligosarcus and this relationship is supported by seven morphological synapomorphies: 1) well developed temporal fossa, 2) absence of a dorsal expansion on the rhinosphenoid, 3) posteroventrally angled articulation between second and third infraorbitals, 4) presence of ectopterygoid teeth on a row, 5) laterally displaced cartilage on the ectopterygoid, 6) presence of bony lamellae bordering laterosensory canal of suprapreopercle, and 7) presence of two pairs of uroneurals. The new species is diagnosed by the following combination of characters: 1) two distinct premaxillary rows of teeth, 2) tricuspidate and pentacuspidate teeth on dentary and posterior premaxillary row, 3) presence of a row of 3–4 tricuspidate to conical ectopterygoid teeth, 4) possession of v-vi,21–23 anal-fin rays, and 5) presence of 41–42 perforated scales on lateral line. Oligosarcus itau n. sp. was previously considered as an Astyanacinus. Astyanacinus moorii (Boulenger), type species of the genus, is included in the Astyanax clade and Astyanacinus platensis Messner is transferred to Oligosarcus.

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A new species of Astyanax (Characiformes, Characidae) from Uruguay river basin in Argentina, with remarks on hook presence in Characidae. -In the present paper the new species Astyanax ojiara sp. n. is described, from the headwaters of Yaboti river, an affluent of Uruguay river in the province of Misiones, Argentinean northeast. A combination of characters differentiates the new species from other congeners: one heptacuspid maxillary teeth; teeth of inner premaxillary row gently expanded distally; 7-9 dentary teeth decreasing in size anteroposteriorly; males with hooks in all fins; large males with pelvic axillary scale bearing | to 8 hooks; 36-38 perforated scales in lateral line; 20-23 branched anal-fin rays. Number of scales in the lateral line and branched anal-fin rays, humeral spot, and low body of Astyanax ojiara sp. n. resemble those of A. eigenmanniorum, but maxillary, premaxillary and dentary teeth differ in both species. The disposition of the dentary teeth is also similar in A. taeniatus and A. giton but A. ojiara sp. n. has one heptacuspid maxillary tooth.

Chrysobrycon eliasi is described from several drainages of río Madre de Dios and upper río Manuripe basins, río Madeira basin, Peru. The new species is distinguished from its congeners by the maxillary teeth, which are tricuspidate, bicuspidate and conical, and the terminal lateral-line tube developed between caudal-fin rays 10-11. Other characters that help to recognize C. eliasi are the possession of maxilla with 6-15 (usually 11) teeth occupying more than 70% of the length of the maxilla in adults, predorsal scales 18-22, dorsal-fin to hypural complex length 36.32-41.17% of standard length (SL), gill-gland length in males 3.57-5.05% SL, maxillary length 33.76-38.75% of head length, and branched anal-fin rays 24-30. The discovery of C. eliasi allows us to extend the geographic distribution of the genus to the southeast, into the río Madeira basin.Chrysobrycon eliasi se describe para varios drenajes en las cuencas de los ríos Madre de Díos y Alto Manuripe, cuenca del río Madeira, Peru. La nueva especie puede diferenciarse de sus congéneres por la presencia de dientes maxilares, que son tricuspidados, bicuspidados y cónicos, y el tubo terminal de la línea lateral desarrollado entre los radios caudales 10-11. Otros caracteres que ayudan a reconocer C. eliasi son la presencia de 6-15 (usualmente11) dientes maxilares ocupando más del 70% de la longitud de la maxila en adultos, escamas predorsales 18-22, longitud origen aleta dorsal-hipurales 36,32-41,17% de longitud estandard (LE), longitud de la glándula branquial en machos 3,57-5,05% LE, longitud de la maxila 33,76-38,75% de longitud de la cabeza, y radios ramificados en la aleta anal 24-30. El hallazgo de C. eliasi nos permite ampliar la distribución geográfica del género hacia el sureste en la cuenca del río Madeira.

The family Sciaenidae comprises about 300 species. The black drum Pogonias cromis was the only valid species of the genus. Herein, Pogonias courbina Lacepède 1803 is redescribed based on morphological and molecular evidence and a neotype is designated. Pogonias courbina is distinguished by the following characters: the occurrence of characteristic thickening of the dorsal spines VII to XI in all specimens larger than 250 mm SL; all pterygiophores in the dorsal-fin laminar, thin; anal-fin pterygiophores slender excluded those of spines; lateral projections of gas bladder with few finger-like projections; genetic distance between both species 1%; exclusive occurrence of characters in six informative sites of COI (58 G; 214 G; 328 A; 331 A; 553C; 580 G). The method Automatic Barcode gap Discovery detected gaps in nucleotid distance congruent with the NJ, MP, and ML tree analysis. Also, advertisement calls are three times shorter in duration in P . courbina than in P . cromis . In addition, two monophyletic groups for P . cromis and P . courbina appear in trees obtained with different methodologies, emphasizing the absence of shared haplotypes. A gap of about 8000 km occurs in the distribution of both species along coastal areas of the Atlantic Ocean.

Pimelodus albicans Valenciennes, 1840 (common name "moncholo" or "bagre blanco") is an endemic species of the family Pimelodidae in the río de la Plata basin. Phylogenetic approach based on cytochrome b sequences was performed to test the existence of a unique evolutionary lineage in P. albicans and to discriminate populations units or subpopulations related to a migration behavior of this taxon in the río de la Plata basin. This study included 34 samples of P. albicans of different collecting sites in the río de la Plata estuary and in the río Arrecifes belonging to the río Paraná basin. Among 614 base pairs in the cytochrome b sequence data set, 203 were variable and 120 were phylogenetically informative sites in P. albicans. A total of twenty haplotypes, nucleotide diversity ( ) = 0.032 and haplotype diversity = 0.941 were found. Tajima's test showed significant value D= -1.88 (p<0.05) rejecting the neutral mutation hypothesis for the P. albicans data set. All phylogenetic approaches showed that P. albicans included four monophyletic assemblages that were supported by high bootstrap and Bayesian posterior probability values. Minimum spanning network corroborated these groups for P. albicans haplotypes. High genetic structure was found in P. albicans by means of AMOVA analysis showing that the río Arrecifes samples constitute an isolated lineage. Moreover, the high value of genetic divergence (10%) between the río de la Plata and the río Arrecifes populations could suggest that P. albicans may be conformed by a sibling species complex. On the other hand, a degree of genetic structuring was detected among different sites of the río de la Plata. A partial isolation of the 760 site may suggest that P. albicans could migrates to different tributaries for reproduction, generating different schools of haplotypes which could mix in the río de la Plata estuary. The high nucleotide diversity found in the 765 site and the existence of gene flow with the remaining collecting sites would be concordant with the outlined hypothetic scenarios of the mixing populations in the middle of the río de la Plata estuary.Pimelodus albicans Valenciennes, 1840 (popularmente conhecida como moncholo ou bagre branco) é uma espécie endêmica da família Pimelodidae na bacia do rio da Prata. Estudos filogeográficos baseados nas seqüências do citocromo b mitocondrial foram realizados para testar a existência de uma única linhagem evolutiva in P. albicans e para discriminar unidades populacionais relacionadas ao comportamento migratório desse táxon na bacia do rio da Prata. Um total de 34 amostras de P. albicans provenientes de diferentes lugares de coleta no estuário do rio da Prata e rio Arrecifes na bacia do rio Paraná foram analisados. Entre as 614 pares de bases do citocromo b no conjunto de dados, 203 deles variaram e 120 foram sítios filogeneticamente informativos para P. albicans. No presente estudo foi encontrado um total de vinte haplótipos, diversidade de nucleotídeos ( ) = 0,032 e diversidade de haplótipos = 0,941. O teste de Tajima...

Two new species of the genus Astyanax (Characiformes, Characidae) from the Parana river basin, in Argentina. -Astyanax leonidas and A. troya are described from the rio Parana basin in northeastern Argentina. Both species share similar number of anal-fin rays and perforated scales in the lateral line, one maxillary tooth, a deep dentary and the presence of small hooks on pectoral, pelvic, anal, and caudal fin of males. These characters are also present in A. ojiara and separate the three species from the remaining species of the genus. Astyanax leonidas is differenciated by the robust body, dorsal profile almost straight, a long and slender maxillary tooth, teeth of premaxillary inner row with notable long central cusp, dentary teeth of similar shape than those of premaxilla, and 4 large dentary teeth followed by one intermediate tooth, and 3 or 4 small teeth. Also this species does not have hooks on dorsal-fin rays and pelvic axillary scale. Astyanax troya has a dorsal profile with marked concavity on supraoccipital area, one broad and low pentacuspid maxillary teeth, teeth of inner premaxillary row gently expanded distally with cusps arising in the same line, central cusp of premaxillary teeth scarcely longer, 8-10 dentary teeth decreasing in size anteroposteriorly, and males with hooks in all fins and pelvic axillary scale.