The annual fish genus Austrolebias is redefined to include species previously placed in Megalebias, and is revised based on characters of osteology, external morphology, the latero-sensory system and color patterns. Monophyly of Austrolebias is supported by the absence of scales between the corner of the mouth and anterior portion of the preopercular region and ventral portion of the opercular region, a deep urohyal, presence of a dark gray supraorbital spot, dorsal and anal fins rounded in males, a long urogenital papilla in males, and reduced ventral process of the angulo-articular. Thirty-eight species are recognized as valid: A. cinereus, A. robustus, A. nonoiuliensis, and A. bellottii, from the lower de La Plata River basin and adjacent areas; A. varzeae, A. melanoorus, A. apaii Costa, Laurino, Recuero & Salvia, new species, A. alexandri, A. ibicuiensis, A. affinis, A. duraznensis, and A. periodicus, from the Uruguay River basin; A. nigripinnis and A. elongatus n. comb., from both the lower de La Plata and Uruguay river basins; A. viarius, A. univentripinnis, A. charrua, A. minuano, A. adloffi, A. nigrofasciatus, A. nachtigalli Costa & Cheffe, new species, A. salviai Costa, Litz & Laurino, new species, A. luteoflammulatus, A. gymnoventris, A. jaegari, A. cheradophilus n. comb., A. wolterstorffi n. comb., and A. prognathus n. comb., A. cyaneus, and A. litzi new species, from the dos Patos lagoon system and adjacent areas to the south; A. vazferreirai, A. arachan, and A. juanlangi Costa, Cheffe, Salvia & Litz, new species, from both the dos Patos lagoon system and Uruguay River basin; A. paranaensis, new species, A. vandenbergi, A. monstrosus n. comb., A. patriciae, from the Paraguay and middle Paraná river basins; and, A. carvalhoi, from the rio Iguaçu basin. A key to the identification of species is provided. A phylogenetic hypothesis based on morphology for species of Austrolebias is compared to a recent hypothesis based on molecular data, demonstrating partial or full congruence between the two sets of characters.

Pterolebias is revised on the basis of osteology, external morphology, latero-sensory system, and color patterns. Two species are recognized as valid: P. longipinnis, from the eastern and southern Amazon River basin and the ParanáParaguay River system, in Brazil, Bolivia, Paraguay and Argentina; and P. phasianus, from the Paraguay River basin, in Brazil and Bolivia. Pterolebias bokermanni and P. luelingi are considered synonyms of P. longipinnis. Monophyly of Pterolebias is corroborated by the morphology of the angulo-articular, second pharyngobranchial, maxilla, metapterygoid, quadrate, basihyal, and two derived color patterns. In contrast to molecular studies, monophyly of an assemblage including Pterolebias and Gnatholebias is herein strongly supported by reduction of the interarcual cartilage, morphology of the anterior proximal radials of the anal fin and pelvic girdle, presence of scale rows on the anal-fin base, derived jaw dentition, numerous pelvic-fin rays, and long pelvic fins. A recent proposal to unite Pterolebias and Gnatholebias in a single genus is rejected.

Trichomycterus comprises about 170 valid species, but its monophyly has been challenged in the last decades. Bayesian Inference and Maximum Likelihood analyses comprehending mitochondrial genes COI and CYTB and nuclear genes GLYT, MYH6 and RAG2 from 71 Trichomycterinae terminal taxa and eight outgroups were performed. The analyses highly supports a clade containing Trichomycterusnigricans, the type species of the genus, and several other congeners endemic to eastern and northeastern Brazil, herein considered as the genus Trichomycterus, the sister clade the southern Brazil and adjacent areas clade; the latter clade comprises two subclades, one comprising species of the genus Scleronema and another comprising species previously placed in Trichomycterus, herein described as a new genus. Cambevagen. n. is distinguished from all other trichomycterines by the presence of a bony flap on the channel of the maxillo-dentary ligament, the interopercle shorter than the opercle, a deep constriction on the basal portion of the antero-dorsal arm of the quadrate, absence of teeth in the coronoid process of the dentary, the maxilla shorter than the premaxilla, the cranial fontanel extending from the the medial posterior of frontal to the medial region of supraoccipital, and absence of the postorbital process of the sphenotic-prootic-pterosphenoid.

Structures of the external morphology and skeleton of the annual fish genera Nematolebias and Simpsonichthys are described and illustrated. Phylogenetic relationships among all included species of both genera and other cynolebiatins are estimated, based on 116 morphological characters in a total of 50 terminal taxa. Nematolebias is hypothesized to be the sister group of a clade including Simpsonichthys, Austrolebias, Megalebias, and Cynolebias, which is diagnosed by ventral portion of mesopterygoid not overlapping quadrate, third neural spine approximately as wide as fourth neural spine, ventral condyle of coracoid narrow, scales slightly extending over anal-fin base, loss of vomerine teeth, loss of neuromast anterior to infraorbital series, ventral process of the angulo-articular short and narrow, and dorsal portion of cleithrum elongated. Simpsonichthys is divided into five subgenera, including Spectrolebias, previously considered a separate genus, Simpsonichthys, and three new subgenera, Xenurolebias, Ophthalmolebias, and Hypsolebias. Monophyly of Simpsonichthys is supported by a small pointed dorsal process on the palatine, unbranched fin rays on the tip of the dorsal and anal fins in males, and frontal E-scales overlapped.Estruturas da morfologia externa e esqueleto dos gêneros de peixes anuais Nematolebias e Simpsonichthys são descritas e ilustradas. Relações de parentesco entre todas as espécies incluídas em ambos gêneros e outros cinolebiatíneos são estimadas, com base em 116 caracteres morfológicos num total de 50 táxons terminais. Nematolebias é considerado como o grupo irmão hipotético de um clado incluindo Simpsonichthys, Austrolebias, Megalebias e Cynolebias, o qual é diagnosticado pela porção ventral do mesopterigóide não se sobrepondo ao quadrado, terceiro espinho neural aproximadamente tão largo quanto quarto espinho neural, côndilo ventral de coracóide estreito, escamas suavemente se estendendo sobre base de nadadeira anal, perda de dentes do vomer, perda de neuromasto anterior à série infra-orbital, processo ventral de ângulo-articular curto e estreito e porção dorsal de cleitro alongada. Simpsonichthys é dividido em cinco subgêneros, incluindo Spectrolebias, anteriormente considerado um gênero separado, Simpsonichthys, e três novos subgêneros, Xenurolebias, Ophthalmolebias e Hypsolebias. Monofiletismo de Simpsonichthys é sustentado por um pequeno processo dorsal pontiagudo no palatino, raios não ramificados na ponta das nadadeiras dorsal e anal em machos e escamas frontais E sobrepostas.

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Aim To analyse the biogeographical events responsible for the present distribution of cynolebiasine killifishes (Teleostei: Rivulidae: Cynolebiasini), a diversified and widespread Neotropical group of annual fishes threatened with extinction.Location South America, focusing on the main river basins draining the Brazilian Shield and adjacent zones.Methods Phylogenetic analysis of 214 morphological characters of 102 cynolebiasine species using tnt, in conjunction with dispersal-vicariance analysis (diva) based on the distribution of cynolebiasine species among 16 areas of endemism. ResultsThe basal cynolebiasine node is hypothesized to be derived from an old vicariance event occurring just after the separation of South America from Africa, when the terrains at the passive margin of the South American plate were isolated from the remaining interior areas. This would have been followed by geodispersal events caused by river-capturing episodes from the adjacent upland river basins to the coastal region. Optimal ancestral reconstructions suggest that the diversification of the tribe Cynolebiasini in north-eastern South America was first caused by vicariance events in the Paranã-Urucuia-São Francisco area, followed by dispersal from the São Francisco to the Northeastern Brazil area. The latter dispersal event occurred simultaneously in two different cynolebiasine clades, possibly as a result of a temporary connection of the São Francisco area before the uplift of the Borborema Plateau during the Miocene. The diversity of cynolebiasines inhabiting the Paraguay area is hypothesized to be derived from two processes: an older vicariance event (about 30 Ma) separating Paraguay from southern Amazonian areas (Guaporé-Xingu-Araguaia-Tocantins), and a series of more recent dispersal and vicariance events (about 15-11 Ma) caused by successive marine transgressions, which permitted alternating biotic exchange and isolation in the Paraguay, La Plata, Negro and Patos areas.Main conclusions diva indicates there to have been a series of vicariance events congruent with tectonic episodes in South America, but the present distribution of cynolebiasines has also been shaped by a series of dispersal events. The effects of the combined action of dispersal and vicariance events were more conspicuous in the Eastern Brazil and Paraguay areas, thus generating reticulate biogeographical scenarios.

A phylogenetic analysis based on morphological characters indicates that Leptolebias Myers, 1952, a genus of small killifishes highly threatened with extinction, from Brazil, is paraphyletic. As a consequence, Leptolebias is restricted in this study to a well‐supported clade that includes Leptolebias marmoratus (Ladiges, 1934), Leptolebias splendens (Myers, 1942), Leptolebias opalescens (Myers, 1942), and Leptolebias citrinipinnis (Costa, Lacerda & Tanizaki, 1988), from the coastal plains of Rio de Janeiro, and Leptolebias aureoguttatus (Cruz, 1974) (herein redescribed, and for which a lectotype is designated) and Leptolebias itanhaensis sp. nov., from the coastal plains of São Paulo and Paraná, in southern Brazil.Leptolebias is diagnosed by three synapomorphies: a caudal fin that is longer than deep, a single anterior supraorbital neuromast, and dark pigmentation that does not extend to the distal portion of the dorsal fin in males. A key is provided for the identification of species of Leptolebias. Three species formerly placed in Leptolebias, Leptolebias minimus (Myers, 1942), Leptolebias fractifasciatus (Costa, 1988), and Leptolebias cruzi (Costa, 1988), are transferred to Notholebias gen. nov., which is hypothesized to be the sister group to the clade comprising Leptolebias, Campellolebias Vaz‐Ferreira & Sierra, 1974, and Cynopoecilus Regan, 1912. Notholebias gen nov. is diagnosed by two synapomorphies: a narrow basihyal and the presence of iridescent bars on the caudal fin in males; and three features interpreted as plesiomorphic, but not occurring in Leptolebias, Campellolebias, or Cynopoecilus, the presence of dermosphenotic, well‐developed contact organs on the pectoral fin in males, and an opercular region with red bars in males. ‘Leptolebias’leitaoi, a species from Bahia, in north‐eastern Brazil, is considered as having an uncertain phylogenetic position, as all known preserved material is presently lost, and the species may be extinct. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 153, 147–160.