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Threadfins are primarily marine bony fishes that have part of the pectoral fin modified into specialized sensitive filaments. They compose the Polynemidae, a family with eight genera and 42 extant species. The internal relationships and phylogenetic position of Polynemidae within Percomorphacea are controversial, with highly conflicting hypotheses proposed by both molecular and phenotypic analyses. We performed a cladistic analysis of threadfins based on the most comprehensive sampling of morphological data ever done. The final dataset included 197 characters from external morphology, the laterosensory system, osteology, myology and neurology in representatives of all valid polynemid genera. More than half of the characters are reported here for the first time, notably the myological ones. A sensitivity analysis of 11 different weighting schemes (equal weighting and extended implied weighting parsimony) resulted in a fully resolved tree. Sciaenidae, not Pleuronectiformes, is recovered as sister to Polynemidae. All polynemid genera are resolved as monophyletic except Polydactylus , which is polyphyletic. Filimanus , Pentanemus and Polydactylus s.s. appear as successive sister taxa of all remaining threadfins. Leptomelanosoma , Parapolynemus and Polynemus form a monophyletic group. Eleutheronema and Galeoides appear intercalated with other species of Polydactylus in the apical portions of the polynemid tree. [ABSTRACT FROM AUTHOR]

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications. [ABSTRACT FROM AUTHOR]

A new species of the poorly known and critically endangered ghost knifefish Tembeassu is described from the upper Paraná and Araguari rivers, Brazil, using external anatomy and X-ray microcomputed tomography (µCT scan). Tembeassu titanicus sp. nov. is distinguished from its sole congener, T. marauna, by a unique set of morphometric and meristic characters, in addition to the absence of a tooth patch at the anterior portion of the roof of the oral cavity and the external corner of the mouth slightly passing the vertical through the posterior margin of the posterior nare. To test the monophyly of Tembeassu and reassess its phylogenetic position, a total-evidence approach was performed through a Bayesian inference (BI) and maximum-parsimony analysis (MP). Our results indicate that Tembeassu is monophyletic and the sister taxon of a clade formed by Apteronotus s.s., Megadontognathus, and Parapteronotus (BI); or as part of a large polytomy at the base of Apteronotidae (MP). Species of Tembeassu co-occur in the Paraná River basin, and the absence of the patch of accessory teeth in T. titanicus sp. nov. may indicate that this species accesses a different food resource, and also putatively occupies a different habitat than T. marauna. Comments on the evolution of the mandibular lobe in Gymnotiformes, dentition pattern in Tembeassu, and apteronotid diversity in the Paraná River are provided. [ABSTRACT FROM AUTHOR]

More than half the ray-finned fishes and about one-quarter of all living vertebrates belong to Percomorphacea. Among its 30 orders, Stromateiformes encompass 77 species in 16 genera and six families. Stromateiform monophyly has never been tested using morphology, and it has been rejected by molecular analyses. This comprehensive revision of Stromateiformes includes all its valid genera of all percomorph families previously aligned with the order. We sampled 207 phenotypic characters in 66 terminal taxa representing 14 orders and 46 acanthopterygian families. This dataset significantly surpasses all previous phenotype-based phylogenies of Stromateiformes, which analysed only a fraction of these characters. Stromateiformes is recovered as monophyletic, supported by eight unequivocal synapomorphies. Amarsipidae is the sister group of all other Stromateiformes (= Stromateoidei). Centrolophidae is paraphyletic, with three of its genera allocated into an early-diverging clade and the other four appearing as successive sister groups to a lineage containing the remaining stromateiforms. All other stromateoid families are monophyletic, with the following cladistic arrangement: (Nomeidae (Stromateidae (Tetragonuridae, Ariommatidae))). Our analysis convincingly refutes recent molecular phylogenetic interpretations that fail to recover a monophyletic Stromateiformes. These findings call into question large-scale conclusions of percomorph relationships and trait evolution based solely on molecular data. [ABSTRACT FROM AUTHOR]

A new species of ghost knifefish is described from the Rio Uatumã at Cachoeira do Miriti, Amazon basin, Brazil. It is distinguished from all species of Apteronotus by the absence of a clear stripe from the chin to the dorsal portions of the head and/or dorsum, a reduced number of anal-fin rays (118-122), and by having four branchiostegal rays. More specifically, the new species resembles Apteronotus quilombola by the low number of anal-fin rays; however, the number of branchiostegal rays and several additional counts and measurements differentiate the species. Furthermore, the new species co-occurs with A. lindalvae, and it can be distinguished by the number of premaxillary teeth. The occurrence area of the new species was highly impacted after the construction of Balbina dam. Thus, considering the threats to the species and the restricted area of distribution, its conservation status was assessed as critically endangered. [ABSTRACT FROM AUTHOR]

A new species of the bluntnose knifefish genus Brachyhypopomus Mago-Leccia is described from headwaters of upper Rio Juruena, and upper Rio Machado, Amazon basin, Brazil. The new species differs from all congeners by the absence of a small independent ossification of the Weberian complex located posterodorsally to the supraoccipital. It can be additionally distinguished from its congeners by a set of characters in combination that includes: absence of accessory electric organ over the opercular region, absence of a prominent pale uninterrupted middorsal stripe on body, presence of scales on the entire middorsal region of body, dorsal rami of the recurrent branch of anterior lateral-line nerve not externally visible, presence of a dark suborbital stripe, and possession of 8–10 scale rows above the lateral line. The phylogenetic position of the new species is inferred by its inclusion in a total-evidence matrix with data from morphology, mitochondrial genes, and nuclear genes of all species. The new species is apparently restricted to upland tributaries of the Chapada dos Parecis, more than 500 m high. Comments on the occurrence of fish species in multiple independent basins at Chapada dos Parecis are also provided. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Astyanax brucutu is a peculiar species of Neotropical tetra endemic from the Chapada Diamantina, a large plateau in northeastern Brazil. Individuals of this species undergo a dramatic ontogenetic shift in their diet that is accompanied by equally remarkable changes in their feeding apparatus. Whereas juveniles of A. brucutu feed mostly on algae, adults feed almost exclusively on an endemic species of hydrobiid snail and other associated living organisms that inhabit their dead shells (including infaunal invertebrates and algae). Skeletal adaptations associated with this change in diet were previously reported, but until now, the changes in the musculature remained mostly unknown. The present paper describes the facial and gular muscles, as well as the buccal ligaments of A. brucutu in different life stages, and identifies the major ontogenetic changes in these systems associated with the diet shift in the species. Such changes primarily involve expansions of specific portions of the adductor mandibulae and associated tendons and ligaments that likely represent adaptations to increase the biting power necessary to crush copious amounts of shells ingested by larger individuals of A. brucutu. Those adaptations are absent in specimens of any size of Astyanax cf. fasciatus, a sympatric congener lacking durophagous feeding habits. Anatomical comparisons and landmark‐based principal components analysis (PCA) suggest that most specializations to durophagy in A. brucutu arose by peramorphosis. We also found that several of the muscular specializations of adults of A. brucutu are paralleled in species of Creagrutus and Piabina, two other characid genera distantly related to Astyanax, but that also feed on hard food items. [ABSTRACT FROM AUTHOR]

In a seminal study on elasmobranch systematics, Maisey proposed the monophyly of a large lineage of sharks based primarily on the sharing of an orbitostylic jaw suspension. This group was later redefined as the Squalomorphi, which included Squatinidae but not Batoidea. Subsequent morphological analyses, however, rejected Maisey's scheme, which was left aside for nearly two decades until the first molecular phylogenies began to cluster again the orbitostylic sharks into a monophyletic group. In a broad comparative investigation of the anatomy of the appendicular skeleton of cartilaginous fishes, we discovered new evidence supporting the monophyly of squalomorph sharks: the presence of a posterior process at the lateral region of the coracoid bar serving as a origin site for the depressor pectoralis II muscle. This feature would be the first strong morphological evidence in 40 years potentially supporting the monophyly of Squalomorphi. [ABSTRACT FROM AUTHOR]

The lateral-line system has been traditionally recognized as an important source of phylogenetic information for different groups of fishes. Although extensively studied in Siluriformes and Cypriniformes, the lateral-line system of Characiformes remained underexplored. In the present study, the anatomy of the cephalic lateral-line canals of characiforms is described in detail and a unifying terminology that considers the ontogeny and homologies of the components of this system is offered. Aspects of the arrangement of lateral-line canals, as well as the number, location and size of canal tubules and pores, resulted in the identification of novel putative synapomorphies for Characiformes and several of its subgroups. The study also revised synapomorphies previously proposed for different characiform families and provided comments on their observed distribution across the order based on extensive taxon sampling. Information from the ontogenetic studies of the cephalic lateral-line canal system and a proposal for the proper use of these data to detect truncations in the development of the lateral-line canals across the order is also offered. [ABSTRACT FROM AUTHOR]

A detailed osteological study of the poorly known and critical endangered ghost knifefish, Tembeassu marauna, from the rio Paraná, Brazil, was conducted using X-ray microcomputed tomography (μCT scan). A redescription of the external anatomy was performed, including the unusual presence of a rostral patch of extra teeth on the region of the upper lip anterior to the premaxilla and the prominent anterior fleshy expansions in both upper and lower lips. The newly surveyed characters were included and analyzed in light of a recent morphological data matrix for Gymnotiformes. In spite of some uncertainties that remains as to phylogenetic allocation of the genus, the most probable hypothesis is that Tembeassu is the sister group of a clade that includes Megadontognathus and Apteronotus sensu stricto. The phylogenetic analysis also supports that Tembeassu is considered a valid genus of Apteronotidae. An amended diagnosis for the genus is also provided. [ABSTRACT FROM AUTHOR]

The muscles serving the ventral portion of the gill arches ( = infrabranchial musculature) are poorly known in bony fishes. A comparative analysis of the infrabranchial muscles in the major percomorph lineages reveals a large amount of phylogenetically-relevant information. Characters derived from this anatomical system are identified and discussed in light of current hypotheses of phylogenetic relationships among percomorphs. New evidence supports a sister-group relationship between the Batrachoidiformes and Lophiiformes and between the Callionymoidei and Gobiesocoidei. Investigated data also corroborate the existence of two monophyletic groups, one including the Pristolepididae, Badidae, and Nandidae, and a second clade consisting of all non-amarsipid stromateiforms. New synapomorphies are proposed for the Atherinomorphae, Blenniiformes, Lophiiformes, Scombroidei (including Sphyraenidae), and Gobiiformes. Within the latter order, the Rhyacichthyidae and Odontobutidae are supported as the successive sister families of all remaining gobiiforms. The present analysis further confirms the validity of infrabranchial musculature characters previously proposed to support the grouping of the Mugiliformes with the Atherinomorphae and the monophyly of the Labriformes with the possible inclusion of the Pholidichthyiformes. Interestingly, most hypotheses of relationships supported by the infrabranchial musculature have been advanced by preceding anatomists on the basis of distinct data sources, but were never recovered in recent molecular phylogenies. These conflicts clearly indicate the current unsatisfactory resolution of the higher-level phylogeny of percomorphs. [ABSTRACT FROM AUTHOR]

Bony fishes of the morphologically diverse infraclass Teleostei include more than 31 000 species, encompassing almost one-half of all extant vertebrates. A remarkable anatomical complex in teleosts is the adductor mandibulae, the primary muscle in mouth closure and whose subdivisions vary in number and complexity. Difficulties in recognizing homologies amongst adductor mandibulae subdivisions across the Teleostei have hampered the understanding of the evolution of this system and consequently its application in phylogenetic analyses. The adductor mandibulae in representatives of all lower teleost orders is described, illustrated, and compared based on broad taxonomic sampling complemented by extensive literature information. Muscle division homologies are clarified via the application of a standardized homology-driven anatomical terminology with synonymies provided to the myological terminologies of previous studies. Phylogenetic implications of the observed variations in the adductor mandibulae are discussed and new possible synapomorphies are proposed for the Notacanthiformes, Ostariophysi, Cypriniformes, Siluriphysi, Gymnotiformes, and Alepocephaloidei. New characters corroborate the putative monophyly of the clades Albuliformes plus Notacanthiformes ( Elopomorpha), Argentinoidei plus Esocoidei plus Salmonoidei ( Protacanthopterygii) and Hemiodontidae plus Parodontidae ( Characiformes). We further confirm the validity of characters from the adductor mandibulae previously proposed to support the monophyly of the Esocoidei and the gonorynchiform clade Gonorynchoidei plus Knerioidei. © 2014 The Linnean Society of London [ABSTRACT FROM AUTHOR]

The infraclass Teleostei is a highly diversified group of bony fishes that encompasses 96% of all species of living fishes and almost half of extant vertebrates. Evolution of various morphological complexes in teleosts, particularly those involving soft anatomy, remains poorly understood. Notable among these problematic complexes is the adductor mandibulae, the muscle that provides the primary force for jaw adduction and mouth closure and whose architecture varies from a simple arrangement of two segments to an intricate complex of up to ten discrete subdivisions. The present study analyzed multiple morphological attributes of the adductor mandibulae in representatives of 53 of the 55 extant teleostean orders, as well as significant information from the literature in order to elucidate the homologies of the main subdivisions of this muscle. The traditional alphanumeric terminology applied to the four main divisions of the adductor mandibulae – A1, A2, A3, and Aω – patently fails to reflect homologous components of that muscle across the expanse of the Teleostei. Some features traditionally used as landmarks for identification of some divisions of the adductor mandibulae proved highly variable across the Teleostei; notably the insertion on the maxilla and the position of muscle components relative to the path of the ramus mandibularis trigeminus nerve. The evolutionary model of gain and loss of sections of the adductor mandibulae most commonly adopted under the alphanumeric system additionally proved ontogenetically incongruent and less parsimonious than a model of subdivision and coalescence of facial muscle sections. Results of the analysis demonstrate the impossibility of adapting the alphanumeric terminology so as to reflect homologous entities across the spectrum of teleosts. A new nomenclatural scheme is proposed in order to achieve congruence between homology and nomenclature of the adductor mandibulae components across the entire Teleostei. [ABSTRACT FROM AUTHOR]

Abstract: The Characiformes are distributed throughout large portions of the freshwaters of Africa and America. About 90% of the almost 2000 characiform species inhabit the American rivers, with their greatest diversity occurring in the Neotropical region. As in most other groups of fishes, the current knowledge about characiform myology is extremely poor. This study presents the results of a survey of the mandibular, hyopalatine, and opercular musculature of 65 species representing all the 18 traditionally recognized characiform families, including the 14 subfamilies and several genera incertae sedis of the Characidae, the most speciose family of the order. The morphological variation of these muscles across the order is documented in detail and the homologies of the characiform adductor mandibulae divisions are clarified. Accordingly, the mistaken nomenclature previously applied to these divisions in some characiform taxa is herein corrected. Contradicting some previous studies, we found that none of the examined characiforms lacks an A3 section of the adductor mandibulae, but instead some taxa have an A3 continuous with A2. Derived myological features are identified as new putative synapomorphies for: the Characoidei; the clade composed of the Alestidae, Characidae, Gasteropelecidae, Cynodontoidea, and Erythrinoidea; the clade Cynodontoidea plus Erythrinoidea; the clade formed by Ctenoluciidae and Erythrinidae; the Serrasalminae; and the Triportheinae. Additionally, new myological data seems to indicate that the Agoniatinae might be more closely related to cynodontoids and erythrinoids than to other characids. [Copyright &y& Elsevier]

Trichomycteridae is the second most diverse family of the order Siluriformes, its members are widely distributed through the freshwaters of Central and South America, exhibiting an exceptional ecological and phenotypic disparity. The most diverse subfamily, Trichomycterinae, represented mainly by the genus Trichomycterus , historically has been recognized as non-monophyletic and various characters used to unite or divide its constituents are repeatedly called into question. No comprehensive molecular phylogenetic hypothesis regarding relationships of trichomycterids has been produced, and the present study is the first extensive phylogeny for the family Trichomycteridae, based on a multilocus dataset of three mitochondrial loci and two nuclear markers (3284 bp total). Our analysis has the most comprehensive taxon-sampling of the Trichomycteridae published so far, including members of all subfamilies and a vast representation of Trichomycterus diversity. Analysis of these data showed a phylogenetic hypothesis with broad agreement between the Bayesian (BI) and maximum-likelihood (ML) trees. The results provided overwhelming support for the monophyletic status of Copionodontinae, Stegophilinae, Trichomycterinae, and Vandelliinae, but not Sarcoglanidinae and Glanapteryginae. A major feature of our results is the support to the current conceptualization of Trichomycterinae, which includes Ituglanis and Scleronema and excludes the “Trichomycterus” hasemani group. Divergence time analysis based on DNA substitution rates suggested a Lower Cretaceous origin of the family and the divergence events at subfamilial level shaped by Paleogene events in the geohistory of South America. This hypothesis lays a foundation for an array of future studies of evolution and biogeography of the family. [ABSTRACT FROM AUTHOR]