A new species of Curimatopsis Steindachner (Characiformes: Curimatidae) from the Rio Nhamundá, Amazon basin

A new species of Curimatopsis is described from the Rio Nhamundá, Amazon basin in northern Brazil. The new species is distinguished from congeners by the presence of a distinctive concentration of dark pigmentation over the entire lower lobe of the caudal fin, reticulate pattern of body pigmentation, lower jaw longer than and overlapping the anterior portion of the upper jaw, crescent‐shaped posterior nostril and by morphometric and meristic data. Comments on the phylogenetic position of the new species within Curimatopsis are also provided.     

A new species of Centromochlus (Siluriformes,Auchenipteridae, Centromochlinae) from the middle Rio Tocantins basin,Brazil

A new species of the catfish genus Centromochlus (Auchenipteridae, Centromochlinae) is described. The new species is diagnosed by having numerous dark rounded blotches over the body and fins, dorsal‐fin spine with serrations anteriorly and smooth posteriorly, anal fin of mature males with three unbranched and seven branched rays, anterior nuchal plate absent and posterior nuchal plate not extended ventrally. The new species is described from a small stream in the Estação Ecológica Serra Geral de Tocantins, a natural reserve in the centre of the Brazilian Cerrado, close to the watershed between the Rio Tocantins and the Rio São Francisco basins. The new species is possibly the sister taxon to the recently described Centromochlus meridionalis from the upper Rio Tapajós. Those two species share with Centromochlus perugiae, from the upper Amazon and upper Paraguay, derived features associated with the modified anal fin in sexually mature males.     

Knodus dorsomaculatus (Characiformes: Characidae), a new species from Teles Pires River,Tapajós River basin,Brazil

Knodus dorsomaculatus, a new species, is described from Teles Pires River, a tributary of the Tapajós River, Brazil. It can be distinguished from its congeners by the presence of a conspicuous dark blotch on the base of the first five branched dorsal fin rays and the presence of ii,9 dorsal fin rays. Additional comparisons between K. dorsomaculatus and its congeners are presented.     

Two new species of Hyphessobrycon (Characiformes: Characidae) from the headwaters of the Tapajós and Xingu River basins,Pará, Brazil

Two new species of Hyphessobrycon are described from the headwaters of the Tapajós and Xingu River basins, Pará, Brazil. Both new species can be distinguished from congeners by the presence of a vertically elongate humeral blotch, a conspicuous round to vertically oblong caudal‐peduncle blotch not extending onto the distal portions of the middle caudal‐fin rays, a conspicuous blotch on the central portion of the third infraorbital immediately ventral to the eye, the lack of a conspicuous longitudinal stripe and the lack of sexual dimorphism in the extension of the caudal‐peduncle blotch. Hyphessobrycon delimai n. sp. can be distinguished from Hyphessobrycon krenakore n. sp. by the extent of the caudal‐peduncle blotch which extends across most of the caudal‐peduncle depth (v. restricted to the middle portion of the caudal peduncle), the presence of dark chromatophores uniformly scattered along the length of the interradial membranes of the dorsal, anal and caudal fins (v. concentrated on the distal one‐half or one‐fourth of the interradial membranes) and the absence of small bony processes on the pelvic and anal fins of mature males (v. small bony processes present).     

New species of Moenkhausia Eigenmann (Characiformes: Characidae) from Rio Xingu and Rio Tapajós basins,Brazil, with comments on a putative case of polymorphic Batesian mimicry

A new species of Moenkhausia is described from Rio Xingu and Rio Tapajós basins, Brazil. The new species is distinguished from its congeners, except from Moenkhausia moisae, by having more scales in the lateral series, 43–47 (v. 23–41 in the remaining congeners). The new species is distinguished from M. moisae by its colour pattern, which consists of a dark midlateral stripe, and an asymmetrical caudal blotch (inconspicuous or faded in specimens from the Rio Arinos) continuous with the midlateral stripe (v. narrow dark midlateral line and conspicuous, regularly rounded and symmetrical blotch not continuous with the midlateral line). The new species is putatively assumed to be mimetic to Jupiaba apenima, in the Rio Xingu and Rio Teles Pires drainages, and to Jupiaba yarina in the Rio Arinos. The two species of Jupiaba are sympatric and remarkably similar in size, general external morphology and colouration to the new species. A small difference occurs in the colouration between the two species of Jupiaba and is also observed in the two respectively sympatric morphotypes of the new species of Moenkhausia. The occurrence of polymorphic Batesian mimicry is therefore discussed for neotropical freshwater fishes.     

A new species of miniature Characidium (Characiformes: Crenuchidae) from the upper Rio Paraguay basin,Mato Grosso state,Brazil

A new miniature species of Characidium is described from the upper Rio Paraguay basin, Brazil. The new species can be diagnosed from all congeners by the presence of a dark-brown humeral blotch, vertically elongated (spanning 5 to 7 horizontal scale rows), with the shape of an upside-down acute triangle. Additionally, it can be diagnosed by a short lateral line (6 to 8 perforated scales), the absence of a conspicuous peduncular blotch, a lower number of principal caudal-fin rays (14–16) and by absence of the adipose fin. The new species is the smallest species of the genus; the largest specimen was 19.3 mm standard length.     

New remarkable sexually dimorphic miniature species of Hyphessobrycon (Characiformes: Characidae) from the upper Rio Tapajós basin

A new miniature species of Hyphessobrycon is described from an affluent of the Rio Papagaio, tributary of the Rio Juruena, upper Rio Tapajós basin, Mato Grosso State, Brazil. The new species can be distinguished from its congeners by having a remarkable secondary sexual dimorphism in its live colouration (males are red and females yellow), well‐defined and relatively narrow dark midlateral stripe extending from tip of snout to tip of middle caudal‐fin rays, absence of humeral blotch, 15–18 branched anal‐fin rays and five or six branched pelvic‐fin rays. The sexually dimorphic colouration of the new species is briefly discussed regarding its temporal variation.     

A new species of the leopard pleco genus Pseudacanthicus (Siluriformes: Loricariidae) from the Rio Xingu,Brazil

The genus Pseudacanthicus comprises six valid species distributed in the Amazon basin and Caribbean coastal drainages from Guyana to French Guiana: P. serratus, P. fordii, P. histrix, P. spinosus, P. leopardus and P. pitanga. A new species of Pseudacanthicus is described from the Rio Xingu Basin, distinguished from its congeners by the following combination of characters: presence of anastomose dark blotches forming continuous zigzag bands alongside longitudinal keels; presence of dark blotches on ventral surface of body and head; all fins with orange to red colour on unbranched rays and sometimes subsequent branched rays. Brief comments on ornamental fisheries and conservation of the new species are also provided.     

A new species of Astyanax (Characiformes: Characidae) from Dolina Água Milagrosa,Rio Paraguai basin,Mato Grosso,Brazil

A new species of Astyanax is described from the upper Rio Paraguai basin, Mato Grosso State, Brazil. The new species can be distinguished from congeners by having the body intensely yellowish in life (v. silvery, reddish or lightly yellow) and by morphometric and meristics traits. Astyanax dolinae n. sp. cannot be assigned to any of the Astyanax species complex currently recognized for the genus. It is only known from the Dolina Água Milagrosa, a karstic sinkhole lake, entirely fed by groundwater, surrounded by Cerrado, the savannah‐like vegetation of central South America.     

A new species of Rhinopetitia Géry 1964 (Ostariophysi: Characiformes: Characidae) from the Rio Teles Pires,Rio Tapajós basin,Brazil

A new species of Rhinopetitia is described from the Rio Teles Pires, a major tributary of the Rio Tapajós. The new taxon is distinguished from its only congener, Rhinopetitia myersi, by having all premaxillary teeth in both rows with seven to nine cusps, maxillary teeth with seven or eight cusps, a distinct dark midlateral stripe on the body and a round humeral blotch (v. outer series of premaxillary teeth with three cusps and inner series of premaxillary teeth with three to five cusps, maxillary teeth with three to five cusps, the absence of a dark midlateral stripe and humeral blotch). Putative characters suggesting a close relationship between Rhinopetitia, Bryconacidnus, Ceratobranchia, Monotocheirodon, Odontostoechus, Othonocheirodus and Rhinobrycon are presented. This putative clade is included in the Stevardiinae, a monophyletic group within the Characidae.     

A new endangered species of Megaleporinus (Characiformes: Anostomidae) from the Rio de Contas basin,eastern Brazil

A new species of Megaleporinus is described from the Rio de Contas, a coastal drainage of eastern Brazil, and its phylogenetic relationships are studied using molecular data. The new species is unique among Anostomidae by possessing two exclusive features: an irregular dark longitudinal stripe from supracleithrum to second midlateral blotch and anterior cranial fontanel partially closed. In addition, the new species is diagnosed by having three premaxillary teeth, three dentary teeth, 37 or 38 scales in lateral line, 16 scale rows around caudal peduncle, three dark midlateral blotches on body, and red fins in life. The new species is closely related to M. obtusidens from the São Francisco basin, corroborating previous studies that indicated that the latter represents a species complex as currently defined. The new species exhibits the first rib enlarged in mature males, a feature described for some congeners. The new species is herein considered to be Endangered under the IUCN criteria.     

A new species of Hyphessobrycon (Characiformes,Characidae) from the upper Rio Jequitinhonha basin,Minas Gerais,Brazil, with comments on morphological similarities with Stethaprioninae species from headwater environments

A new species of Hyphessobrycon is described from a marshland area in the headwaters of Rio Jequitinhonha basin, Minas Gerais, Brazil. The new species differs from congeners by presenting a single well-delimited conspicuous humeral blotch, rounded to vertically oval, restricted to the area dorsal to the lateral-line row of scales, without a narrower downward extension, greatest body depth anterior to dorsal-fin origin, bony processes in anal and pectoral-fin rays of males and four teeth in the inner row of the premaxillary bone. The new species presents a set of morphological features shared by some species currently assigned to Hasemania, Myxiops and to the Astyanax scabripinnis complex. Some of these features are discussed.     

Morphological and molecular evidence for two new species of Tetragonopterus (Characiformes: Characidae) from central Brazil

The combination of morphological and molecular data of Tetragonopterus species collected in the Rio Araguaia basin allows the recognition of two undescribed species that are presented in this article. These species are distinguished from their congeners (Tetragonopterus anostomus, Tetragonopterus argenteus, Tetragonopterus carvalhoi, Tetragonopterus chalceus and Tetragonopterus rarus) by characters related to the number and morphology of the teeth, the numbers of gill rakers on the upper and lower limbs of the first gill arch, the number of predorsal scales and the overall colour pattern. In addition, the analysis of mitochondrial DNA sequences identified an accentuated genetic distance between these two new species and their congeners. A discussion of the phylogenetic relationships within Tetragonopterus is provided.     

Phylogenetic study of the Characinae (Teleostei: Characiformes: Characidae)

The Characinae is a subunit of the Characidae of special significance in including Charax, the type genus of the family and the order Characiformes. Twelve genera and 79 species have been traditionally assigned to the Characinae, but the subfamily still lacks a phylogenetic diagnosis. Herein, a data matrix including 150 morphological characters and 64 taxa (35 species representing all genera of the Characinae and 29 included in other lineages within the Characiformes) was submitted to two cladistic analyses that differ in the inclusion/exclusion of Priocharax due to the difficulty of coding most of the character states in the miniature species of this genus. Both analyses resulted in a non‐monophyletic Characinae and this subfamily is herein restricted to only seven of the original 12 genera forming the clade (Phenacogaster((Charax Roeboides)(Acanthocharax(Cynopotamus(Acestrocephalus Galeocharax))))), which is supported by ten non‐ambiguous synapomorphies and is more closely related to other genera of the Characidae than those traditionally placed in the subfamily. A second clade includes the members of the tribe Heterocharacini (Lonchogenys(Heterocharax Hoplocharax)) as the sister‐group of Gnathocharax, supported by seven non‐ambiguous synapomorphies. This clade is more closely related to a taxon formed by Roestes and Gilbertolus based on seven non‐ambiguous synapomorphies. Results do not corroborate a close relationship between Roestes–Gilbertolus and the Cynodontinae. Inclusion of the genus Priocharax suggests that it is related more closely to the Heterocharacini, but the profound modifications in its anatomy possibly related to ontogenetic truncations obscure a better understanding of its relationships. A new classification of the Characinae and the Heterocharacinae is proposed. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 165 , 809–915.     

A new species of Astyanax Baird & Girard (Characiformes: Characidae) from the Rio Paraguaçu basin,Chapada Diamantina,Bahia, Brazil,with comments on bony hooks on all fins

A new species of Astyanax from the Rio Paraguaçu basin, Bahia, Brazil, is described. This new species is distinguished from its congeners known to occur in Brazilian drainages by the presence of small bony hooks on all fins of mature males. Furthermore, the new species can be diagnosed by its colour pattern, which consists of a unique vertically elongated humeral blotch, a conspicuous dark drop‐shaped horizontal blotch over the caudal peduncle, tapering anteriorly and not extending to the median caudal‐fin rays, and by the absence of a conspicuous broad dark midlateral stripe. The new species differs further by having the greatest body depth just anterior to the dorsal‐fin origin, 32–35 perforated scales in the lateral line and a reduced number of branched anal‐fin rays (16–20). Apparently, the new species does not fit into any species complex of Astyanax. The occurrence of bony hooks on all fins of Astyanax is discussed.     

A new species of sexually dimorphic and rheophilic ghost knifefish (Apteronotidae: Gymnotiformes) from the Amazon basin

A new species of ghost knifefish, Apteronotus, is described from high-energy environments in the Rios Mapuera and Trombetas (at Cachoeira Porteira waterfalls), Brazil. X-ray microcomputed tomography (μCT scan) was used to access the internal anatomy of the type series. The new species is distinguished from all congeners by the anteriormost position of the anus, with its posterior margin extending less than one eye diameter beyond the vertical through the caudal limit of the posterior nostril, the low number of anal-fin rays (117–125) and the reduced number of branchiostegal rays (three). A series of modifications associated with secondary sexual dimorphism on the preorbital region of mature males are depicted and discussed. In addition, comments on homologies of the branchiostegal rays in Apteronotidae are provided.     

A new species of Astyanax (Characiformes: Characidae) from Costa Rica and Panama,with a key to the lower Central American species of the genus

Astyanax anai, a new species of characid fish, is described from the Sixaola River basin, eastern Costa Rica–western Panama, Central America. The new species can be distinguished from all other congeners by the following combination of characters: premaxillary teeth 4–5 at the inner series and 4–6 at the outer series; maxillary teeth tricuspid, 2–4; predorsal scale series irregular and incomplete, with an unscaled space behind tip of supraoccipital process and 12–14 scales; lateral line scales 34–39; humeral region with a conspicuous black and rounded to horizontally ovate spot and two diffuse brown and vertically elongate bars (the first through the rounded to horizontally ovate spot, the second 2–4 scales behind the first); body depth 36·6–42·3% of standard length (L_S); midlateral stripe formed by a series of 10–14 anteriorly‐directed dermal herringbone, or chevron‐shaped, marks, most apparent in juveniles and in preserved specimens, extending above the lateral line from the black humeral spot or just behind it (from the second vertical bar) to the caudal peduncle; scale rows from lateral line to base of first dorsal‐fin ray 8–9; scale rows from lateral line to base of pelvic fin 7–8; pre‐anal distance 53·9–61·9% of L_S; total anal‐fin elements 29–33; caudal spot elongated, rhomboid or rectangular, with its anterior margin surpassing the middle of the caudal peduncle, usually reaching the anal‐fin insertion, posteriorly covering 4–7 principal caudal‐fin rays and not extending onto the ventral and dorsal margins of the caudal peduncle, covering 3–5 horizontal scale rows. In order to test the phylogenetic relationships of the new taxon in relation to the other North and Central American species of the genus, a new phylogenetic hypothesis based on a reanalysis of the morphological matrix by Schmitter‐Soto (2016) is proposed. A key to the lower Central American (southern Nicaragua to eastern Panama) species of Astyanax is also provided.     

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga,upper Rio Juruena basin,Mato Grosso,Brazil, with a review of sexual dichromatism in Characiformes

Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal‐fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.