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ABSTRACT The history of knowledge about Amazonian biogeography is as rich as its fish community, and a fascinating theme of study in itself. Several current paradigms and controversies about Amazonian fish biogeography are rooted in principles dating from the second half of the 18th to the first half of the 19th centuries. The present work establishes a relationship between current biogeographical ideas and their old predecessors, on the basis of a chronologically-oriented historical continuity analysis. The advent of evolutionary theory has not contributed significantly to a transformation of the knowledge on the biogeography of Amazonian fishes. On the other hand, the two main schools of biogeographical thought (dispersalist and vicariant) had major implications on how Amazonian fish distribution is interpreted. The process was gradual and many hypotheses have combined elements from each of the two schools. Chronologically, practically the entire tradition of Amazonian biogeography takes place within the evolutionary paradigm, although its founder Louis Agassiz was himself an anti-evolutionist. The birth of Amazonian biogeography is Agassiz´s travel in Amazon. That document makes it clear that the author did not consider dispersal as a valid explanation for the biogeographical patterns he found. Later, Carl Eigenmann helps to spread the dispersalist tradition as a model for biogeographical explanations in fish distributions, a phase which lasted until the late 20th century. A major shift occurs with the contributions of Marylin Weitzman, Stanley Weitzman and Richard Vari, who associated the temporal framework of phylogenetic hypotheses with distribution patterns, underscoring the predictive power of vicariant biogeography. The present-day paradigm begins with the work of John Lundberg and attempts to incorporate geomorphological and phylogenetic information into integrative biogeographical hypotheses. Some emblematic problems have delayed proposition of general hypotheses on the phylogenetic biogeography of South American fishes, such as the poor state of knowledge of their species-level systematics; an incomplete distributional record for most species and sparse or non-existent data on the phylogenetic history of most supraspecific taxa. Such drawbacks are now being corrected at a fast pace. Recent advances on geographical distribution and an increasing number of phylogenetic hypotheses will allow unprecedented large-scale biogeographic analyses, including those based on event models and Bayesian inference. Thus, the biogeography of South American fishes, especially Amazonian ones, should soon experiment a new age of progress. The success of that new phase will depend on its ability to recognize and segregate multiple overlapping temporal layers of hydrological changes, and to develop analytical tools that can deal with temporal mixing.

The genus Listrura, Glanapteryginae, currently comprises six valid species of small and elongated trichomycterid catfishes that inhabit coastal plains of Southern and Southeastern Brazil. As primarily fossorial dwellers, species of the genus display unusual morphological adaptations and restricted habitats, which make these fishes particularly susceptible to environmental disturbance. Listrura camposi is poorly known and ranked as a Critically Endangered catfish species, according to current Brazilian list of threatened species. Description of the species was based on a single specimen collected in 1940, and for seven decades no additional specimens were reported. As a consequence, basic information about the species is unavailable. Recently, a population of L. camposi was found inhabiting a small stream tributary to rio Ribeira de Iguape basin, São Paulo State, relatively close to the type locality. On the basis of newly collected material, the species is redescribed and the first data on its habitat and ecology are presented. Conservation status is also discussed.O gênero Listrura, Glanapteryginae, compreende atualmente seis espécies válidas de bagres pequenos e alongados que habitam as baixadas costeiras do Sul e Sudeste do Brasil. Principalmente de hábitos fossoriais, as espécies do gênero apresentam adaptações morfológicas incomuns e habitat restrito, o que torna estes peixes particularmente suscetíveis a distúrbios ambientais. Listrura camposi é pouco conhecida e considerada uma espécie Criticamente em Perigo, segundo as mais recentes listas brasileiras de espécies ameaçadas. A descrição da espécie foi baseada em um único exemplar coletado em 1940 e por sete décadas nenhum espécime adicional foi relatado. Como consequência, informações básicas sobre a espécie estão indisponíveis. Recentemente, uma população de L. camposi foi encontrada habitando um pequeno córrego tributário da bacia rio Ribeira de Iguape, estado de São Paulo, relativamente próximo da localidade-tipo. Com base no material coletado recentemente, a espécie é redescrita e os primeiros dados sobre seu habitat e ecologia são apresentados. O estado de conservação também é discutido.

A new species of sand-dwelling catfish genus Pygidianops, P. amphioxus, is described from the Negro and lower Amazon basins. The new species differs from its three congeners in the elongate eel-like body, the short barbels, and the small caudal fin, continuous with the body, among other traits of internal anatomy. The absence of anal fin further distinguishes P. amphioxus from all other Pygidianops species except P. magoi and the presence of eyes from all except P. cuao. The new Pygidianops seems to be the sister species to P. magoi, the two species sharing a unique mesethmoid with a dorsally-bent tip lacking cornua, and a produced articular process in the palatine for the articulation with the neurocranium. Pygidianops amphioxus is a permanent and highly-specialized inhabitant of psammic environments. Additional characters are proposed as synapomorphies of Pygidianops, including a hypertrophied symphyseal joint and associated ligament in the lower jaw; an elongate, laterally-directed, process on the dorsal surface of the premaxilla; and a rotated lower jaw, where the surface normally facing laterally in other glanapterygines is instead directed ventrally. These and other characters are incorporated into a revised phylogenetic diagnosis of Pygidianops.

A new species of the formerly monotypic genus Trichogenes is described from a high-altitude stream of the rio Itapemirim system, an isolated Atlantic drainage in the State of Espírito Santo, southeastern Brazil. Trichogenes claviger, new species, differs from all other trichomycterids by the sexually dimorphic posterior process of the opercle, much elongated in males; the terminal mouth; the deeply bifurcated anterior neural spines and the presence of a large anterodorsal claw-like process on the neural arches of the anterior four free vertebrae. The new species also differs from its only congener, T. longipinnis, by a number of additional traits, including the the lack of branched anal-fin rays in specimens of any size; the broader than long posterior nostril; the deeper head (head depth 72.9-86.6% HL); the presence of a fine dark line along the base of the anal fin; the lack of dark spots on cheeks; the shape of the interopercle; the presence of odontodes on a bony expansion on the posterodorsal margin of the interopercle; the fewer vertebrae (35); the absence of an antorbital; and the fewer pleural ribs (eight). Small juveniles of the new species are also strikingly different from those of all other Trichomycteridae, including T. longipinnis, having a very large lateral eye, an upturned mouth, and compressed head. Trichogenes claviger occurs in shaded sectors of a blackwater sluggish stream with sandy substrate and patchy accumulations of vegetable debris, a habitat markedly different from the rocky torrential environment known for T. longipinnis. A comparison of the internal anatomy of the two species provides the basis for a hypothesis of a monophyletic Trichogenes. Data from the new species further support a sister-group relationship between Trichogeninae and Copionodontinae, as well as the position of that clade as sister group to all remaining Trichomycteridae.

The catfishes of the subfamily Cetopsinae of the Neotropical family Cetopsidae are revised. Four genera, Cetopsidium new genus, Cetopsis, Denticetopsis, and Paracetopsis Bleeker are recognized as valid. Bathycetopsis, Hemicetopsis, and Pseudocetopsis are considered synonyms of Cetopsis and Paracetopsis Eigenmann & Bean and Cetopsogiton synonyms of Paracetopsis. Thirty-seven species are recognized in the Cetopsinae. Cetopsidium includes six species: C. ferreirai, new species, rio Trombetas; C. minutum, Essequibo River; C. morenoi, central and western portions of río Orinoco; C. orientale, coastal rivers of Suriname and French Guiana, and tentatively rio Tocantins and rio Xingu; C. pemon, new species, río Caura, río Caroni, río Meta, and rio Branco; and C. roae, new species, Rupununi River. Cetopsis includes 21 species: C. amphiloxa, río San Juan, río Atrato, and río Patia, western Colombia, and rivers of northwestern Ecuador; C. arcana, new species, rio Tocantins; C. baudoensis, río Baudo; C. caiapo, new species, rio Tocantins; C. candiru, Amazon basin; C. fimbriata, new species, río Truando; C. coecutiens, rio Amazonas, rio Tocantins, and río Orinoco; C. gobioides, upper rio São Francisco, rio Paraná, río Uruguay, and rio Juquiá; C. jurubidae, río Jurubidá; C. montana, new species, western portions of Amazon basin; C. motatanensis, Lago Maracaibo basin; C. oliveirai, Amazon basin; C. orinoco, río Orinoco, río Aroa, and río Yaracuy; C. othonops, río Magdalena and río Sinú; C. parma, western Amazon basin; C. pearsoni, new species, upper portions of rio Madeira; C. plumbea, western portions of rio Amazonas; C. sandrae, new species, rio Tapajós; C. sarcodes, new species, rio Tocantins; C. starnesi, new species, northwestern río de La Plata and southern rio Madeira; and C. umbrosa, new species, western río Orinoco. Cetopsis chalmersi is a synonym of C. gobioides. Cetopsis macroteronema is a synonym of C. plumbea. Denticetopsis includes seven species: D. epa, new species, rio Tocantins; D. iwokrama, new species, Siparuni River; D. macilenta, Potaro River; D. praecox, río Baria; D. royeroi, upper río Negro; D. sauli, upper río Negro; and D. seducta, new species, western portions of rio Amazonas and río Orinoco. Paracetopsis consists of three species: P. atahualpa, new species, río Tumbes, northwestern Peru, and río Zarumilla, southwestern Ecuador; P. bleekeri, río Guayas and río Santa Rosa, south-western Ecuador; and P. esmeraldas, new species, rivers of northwestern Ecuador. Cetopsis ventralis and C. occidentalis are synonyms of Paracetopsis bleekeri. A neotype is designated for Paracetopsis bleekeri. Lectotypes are designated for Cetopsis candiru, Cetopsis chalmersi, and Cetopsis plumbeus.

The genus Listrura, Glanapteryginae, currently comprises six valid species of small and elongated trichomycterid catfishes that inhabit coastal plains of Southern and Southeastern Brazil. As primarily fossorial dwellers, species of the genus display unusual morphological adaptations and restricted habitats, which make these fishes particularly susceptible to environmental disturbance. Listrura camposi is poorly known and ranked as a Critically Endangered catfish species, according to current Brazilian list of threatened species. Description of the species was based on a single specimen collected in 1940, and for seven decades no additional specimens were reported. As a consequence, basic information about the species is unavailable. Recently, a population of L. camposi was found inhabiting a small stream tributary to rio Ribeira de Iguape basin, São Paulo State, relatively close to the type locality. On the basis of newly collected material, the species is redescribed and the first data on its habitat and ecology are presented. Conservation status is also discussed.

ABSTRACT A review is made of the impact of the landmark Ph. D. Thesis of Jonathan N. Baskin from 1973 on the development of the phylogenetics of catfishes and some of its main subgroups and on neotropical ichthyology in general. Baskin's work is the first to propose a hypothesis of relationships for loricarioid catfishes and for the family Trichomycteridae on the basis of explicit Hennigian principles. It is arguably also the first application of phylogenetic methods to any group of neotropical fishes. The hypotheses presented by Baskin covered the monophyly of Siluriformes, the monophyly and relationships of loricarioid families and the relationships of Trichomycteridae (including the monophyly of the family and the relationships among its constituent genera). His discoveries are analyzed in view of the subsequent 40-odd years of progress on the understanding of the phylogeny of the respective groups. The ideas proposed in 1973 have resisted the test of time remarkably well, and a majority of them have been corroborated by additional characters and taxa (including molecular data and several taxa newly discovered in the meantime), as well as by modern quantitative analysis.

Abstract A new miniature tridentine catfish is described from the rio Purus drainage, Amazon basin, Brazil. It differs from all other tridentines in having several unique autapomorphies: conspicuous anteromedial protuberance in the snout; set of symphyseal premaxillary and dentary teeth inclined posteromedially; distal process of the hyomandibula directed anteriorly; rod-like orbitosphenoid ossified only ventral to the optic nerve; mesethmoid cornua inclined ventrolaterally; opercular and interopercular odontodophores separated by a large interspace; basipterygia fused sagittally; and conspicuous dark brown horizontal stripe in the middle of the caudal fin. The new taxon is hypothesized to be sister to the clade formed by Tridensimilis and Tridens. A detailed osteological description of the new taxon is provided based on X-ray microcomputed tomography (µCT-scans) data and on cleared and stained specimens. Our analysis also reveals that “Tridens” brevis, an enigmatic species that has been indecisively assigned to three different tridentine genera over the past 134 years, belongs to Tridentopsis.Consequently, Tridensimilis is a monotypic genus that currently includes only T. venezuelae.

Trichomycterus anhanga is described from the Amazon basin, northern Brazil. The species is diagnosed by the latero-sensory system which is restricted to LL1 and LL2, the pectoral fin with two branched rays, the absence of pelvic fins and girdle, the reduced jaws and pharyngeal dentition, the presence of six to seven interopercular odontodes, the absence of a lateral series of spots, the presence of a small dark spot on the ventral surface of the mandibular symphysis, the narrow comma-shaped palatine, the absence of procurrent rays anterior to the dorsal and anal fins, the position of insertion of the first dorsal-fin pterygiophore and the presence of a single pair of pleural ribs. Trichomycterus anhanga shares with T. hasemani and T. johnsoni a wide cranial fontanel which occupies most of the skull roof. Miniaturization as well as synapomorphies for the T. hasemani group are discussed.