Abstract Pseudanos is a fish genus with cis-Andean distribution in South America. Pseudanos trimaculatus is originally known from the Amazon and Orinoco basins. Three decades ago, a few specimens collected in the Río de la Plata basin were identified as P. trimaculatus, what remained to be confirmed and understood. The aim of this contribution is to analyze these specimens. Consequently, the morphological variation of P. trimaculatus is discussed and updated. Morphometric and meristic data were taken from the specimens and compared with those of the type and non-type specimens of the species. Multivariate analyses of the size-corrected measurements were used to explore the morphological variation. Size-corrected PCA revealed that the specimens collected in the Río de la Plata basin nested with the remaining specimens, being slightly closer to those from the Guaporé, Napo and Uatumã rivers. Measurements such as caudal peduncle depth, body depth, and body width affected more heavily the first components. Cluster analysis did not show well-defined groups based on the hydrogeographic basins. The studied specimens from the Río de la Plata basin are herein confirmed as conspecific with P. trimaculatus. The species is added to the list of fish species shared between the Amazon and Río de la Plata basins. cisAndean cis Andean America basins ago P understood Consequently updated nontype non sizecorrected size corrected Sizecorrected Size Guaporé rivers depth components welldefined well defined

Resumo Neste trabalho descrevemos duas espécies novas de Diapoma, uma do rio Negro, afluente do rio Uruguai, Brasil e Uruguai, e a segunda do rio Iguaçu, Brasil e Argentina. A espécie nova do rio Negro é diagnosticada de suas congêneres pela combinação das seguintes características: uma linha preta, estreita e conspícua restrita ao septo horizontal do corpo, linha lateral incompleta, dentes da série interna da pré-maxila tricuspidados, e baixa altura do corpo na vertical que passa pela origem da nadadeira dorsal (29,3–32,8% SL em machos e 27,7–33,3% SL em fêmeas). A espécie nova do rio Iguaçu é diagnosticada de suas congêneres pela combinação das seguintes características: linha lateral descontínua, nadadeira adiposa não pigmentada de preto, base da nadadeira anal longa (26,5–32,4% SL) e raios médios da nadadeira caudal com uma linha preta longitudinal. Adicionalmente, atualizamos a filogenia molecular do gênero, incluindo novas sequências destas duas espécies novas e de Diapoma thauma. Uma chave de identificação para as espécies de Diapoma é apresentada, modificada de estudo anterior.

Abstract Herein we describe two new species of Diapoma, one from the Negro River, a tributary of the Uruguay River in Brazil and Uruguay, and one from the Iguaçu River, in Brazil and Argentina. The new species from the Negro River basin is distinguished from its congeners by the following combination of characters: a black narrow and conspicuous line restricted to the body horizontal septum, incomplete lateral line, tricuspid teeth in the inner series of the premaxilla, and a lower body depth at vertical through the dorsal-fin origin (29.3–32.8% SL in males and 27.7–33.3% SL in females). The new species from the Iguaçu River basin is distinguished from its congeners by the following combination of characters: a discontinuous lateral line, adipose fin hyaline, longer anal-fin base (26.5–32.4% SL), and a longitudinal black stripe along the median region of caudal-fin rays. Additionally, we updated the molecular phylogeny of the genus, including new sequences from these two new species and Diapoma thauma. An identification key for species of Diapoma is presented, modified from previous study.

Se presenta una hipótesis preliminar de monofilia para las especies de Bryconamericus de la baja América Central, basada en caracteres moleculares de ADNmt, que resulta en el siguiente arreglo de relaciones filogenéticas: (B. emperador (B. gonzalezoi (B. bayano, (B. terrabensis, B. scleroparius)))). Esta hipótesis es preliminar en el contexto filogenético del género, sin embargo, aumenta la probabilidad de que este grupo se constituya en un grupo natural. Se halla concordancia entre la hipótesis de relaciones presentada para las especies de Bryconamericus analizadas aquí y los hallazgos con base en caracteres morfológicos. A través de biogeografia cladística, cladogramas de áreas, cladogramas resueltos de áreas y Análisis de Dispersión-Vicarianza (DIVA) se comprueba que la hipótesis biogeográfica para las especies de Bryconamericus está relacionada con un proceso de dispersión desde el noroeste de América del Sur, que permitió colonizar la baja Centroamérica. Simultáneamente ocurrieron extinciones, y como producto de la reorganización geológica y aislamiento geográfico de las poblaciones, aparece la vicarianza.

A preliminary hypothesis for the monophyly of Bryconamericus species from lower Central America is presented based on an analysis of molecular characters (mtDNA) that results in the following phylogenetic relationships: (B. emperador (B. gonzalezoi (B. bayano, (B. terrabensis, B. scleroparius)))). This hypothesis is a step towards understanding the phylogenetic relationships within the genus, increasing the probability of Bryconamericus being a natural group. The hypothesis of relationships among the analyzed species is congruent with our findings based on morphological characters. Through cladistic biogeography, area cladograms, resolved area cladograms, and Dispersal-Vicariance Analysis (DIVA), the biogeographic hypothesis for species of Bryconamericus is shown to be related to a process of dispersal from Northwestern South America that allowed colonization of lower Central America. Simultaneously, extinction events occurred, and geologic rearrangements caused geographic isolation of populations and vicariance.

We reviewed Bryconamericus species from the Cauca, Magdalena and Ranchería rivers in Colombia using type and new specimens. The geographic distribution of B.caucanus was determined. We determined the morphological variation among Bryconamericus species analyzed using meristic, morphometric and osteological characters. The shape of Bryconamericus was analyzed using principal component analysis (PCA), in which measurements were previously processed to correct for the effect of size. The number of vertebrae differentiated B. caucanus from other species of the Magdalena River (37-39 vs.40-42). Bryconamericus arilepis Roman-Valencia et al 2008 differs from other Río Magdalena Bryconamericus in lateral-line scales (50-54 vs. 34-50) and scales between dorsal-fin origin and lateral line (9-11 vs. 5-8). The index of form (IF) built with PCA confirmed the validity of species that share the same shape: B. caucanus Eigenmann 1913 andB. plutarcoi Roman-Valencia 2001, B. tolimae Eigenmann 1913, B. huilae Roman-Valencia 2003, B. arilepis and Bryconamericus sp. nov. Román-Valencia, Vanegas-Ríos and Ruiz-C. in press, and the 2 groups were distinguishable from each other. An ANOVA showed significant differences in pelvic-fin length among species of Bryconamericus (F = 44.7, p = 0000). Anal-fin length was also useful to distinguish the studied species (F = 44.03, p = 0000). Populations of B. caucanus from the lower Río Cauca show greatest similarity in shape with all other populations from Río Ranchería, upper and lower Cauca, and middle Magdalena. Hemibrycon dentatus andH. decurrens are shown to be synonyms of B. caucanus. We reconfirm the existence of 2 new species of Bryconamericus from Río Sogamoso, in the Río Magdalena basin. The geographical distribution of B. caucanus in the Sinú, Ranchería, Cauca and lower Magdalena river basins is established.

Se analizan las especies de Bryconamericus Eigenmann 1907 para la cuenca de los ríos Magdalena-Cauca y Ranchería, con base en material tipo y no tipo; además se establece la distribución geográfica de B. caucanus. Se emplean caracteres merísticos, morfométricos y osteológicos para definir la variación morfológica entre las especies de Bryconamericus analizadas. La forma de los Bryconamericus se estudió mediante un análisis de componentes principales (ACP), donde las medidas fueron previamente transformadas para corregir el efecto de talla y alometría. El número de vértebras diferenció a B. caucanus de otras especies del río Magdalena (37-39 vs. 40-42). Se encontró que B. arilepis Román-Valencia, Vanegas-Ríos and Ruiz-C. 2008 se distingue de los demás Bryconamericus del río Magdalena por las escamas en la línea lateral (50-54 vs. 34-50) y las escamas entre el origen de la aleta dorsal y la línea lateral (9-11 vs. 5-8). El índice de forma (IF) construido a partir del ACP confirmó las especies que comparten el mismo perfil: B. caucanus Eigenmann 1913 y B. plutarcoi Román-Valencia 2001, B. tolimae Eigenmann 1913, B. huilae Román-Valencia 2003, B. arilepis y Bryconamericus sp. nov. (en prensa), ambos grupos distinguibles entre sí. El análisis de varianza demostró que existen diferencias significativas entre las longitudes de las aletas pélvicas entre las especies de Bryconamericus (F= 44,7; p= 0,000). Se observaron significancias en las longitudes de la aleta anal, al confrontar las especies de Bryconamericus analizadas (F= 44,03; p= 0,000). Las poblaciones de B. caucanus de la parte baja del río Cauca son las que poseen mayor afinidad en forma con las demás poblaciones del río Ranchería, alto y medio Cauca y bajo Magdalena. Se determina que Hemibrycon dentatus y H. decurrens son sinónimos modernos de B. caucanus; se confirma la existencia de 2 especies nuevas para el río Sogamoso, cuenca del río Magdalena, y se establece la distribución geográfica de B. caucanus en la cuenca de los ríos Sinú, Ranchería, Cauca y bajo Magdalena.