RESUMO Uma espécie nova de Hyphessobrycon é descrita do rio Mutum, um afluente do rio Juruena, bacia do rio Tapajós, Brasil. O táxon novo pode ser distinguido de seus congêneres pela presença de uma faixa média-lateral escura bem definida e relativamente estreita no corpo, estendendo-se da cabeça aos raios médios da nadadeira caudal, presença de uma mancha umeral, 13-16 raios da nadadeira anal ramificada (vs. 17-26) e 11-12 séries horizontais de escamas ao redor do pedúnculo caudal. A espécie nova apresenta polimorfismo em relação à presença da nadadeira adiposa. Assim, é apresentada uma discussão sobre esse tipo de polimorfismo em toda a família e suas implicações na sistemática do grupo.

ABSTRACT A new species of Hyphessobrycon is described from the rio Mutum, a tributary of the rio Juruena, rio Tapajós basin, Brazil. The new taxon can be distinguished from its congeners by the presence of a well-defined and relatively narrow dark midlateral stripe on body, extending from head to the middle caudal-fin rays, presence of a humeral blotch, distal profile of the anal fin falcate in males, 13-16 branched anal-fin rays (vs. 17-26), and 11 or 12 horizontal scale rows around caudal peduncle. The new species shows polymorphism regarding the presence of the adipose fin, and a discussion on this type of polymorphism across the family and its systematic implications is presented.

Abstract A taxonomic revision is presented of the genus Paracanthopoma, probably the least-known vandelliine genus at present. The work is based on most of the material available in museums worldwide and includes a major expansion in the knowledge about the genus. Paracanthopoma is circumscribed as a monophyletic group on the basis of nine putatively synapomorphic characters. Evidence is provided for Paracanthopoma and Paravandellia as sister groups and the two genera are comparatively diagnosed. A total of 13 species are recognized in Paracanthopoma, of which nine are new and one is transferred from Paravandellia: Pc. ahriman, new species, Pc. alleynei (Henschel et al., 2021), Pc. carrapata, new species, Pc. cangussu Henschel et al., 2021, Pc. capeta, new species, Pc. daemon, new species, Pc. irritans, new species, Pc. malevola, new species, Pc. parva Giltay, 1935, Pc. saci Dagosta & de Pinna, 2021, Pc. satanica, new species, Pc. truculenta, new species, and Pc. vampyra, new species. The holotype and paratype of Pc. alleynei are found to belong to two different species. The various taxa in Paracanthopoma display a high degree of phenotypic divergence and are diagnosed on the basis of traditional as well as new morphological characters of both external and internal anatomy. Geographical distributions are mapped for each species and an identification key is provided. Preliminary evidence suggests the existence of four main subclades within Paracanthopoma. The first one includes Pc. ahriman, Pc. cangussu, and Pc. irritans. A second subclade comprises Pc. carrapata, Pc. daemon, Pc. parva, and Pc. truculenta. A third clade includes Pc. malevola and Pc. satanica and a fourth comprises Pc. alleynei and Pc. vampyra. The last clade lacks some putative synapomorphies of all other members of Paracanthopoma and seems to be the sister group to the rest of the genus. Relationships of Pc. capeta and Pc. saci are not as clear, but some evidence exists for the former being related to the first subclade and the latter to the second subclade.

Resumo A Lista Vermelha (IUCN) fornece avaliações precisas sobre status de conservação das espécies, porém a taxa e escala de deterioração ambiental desafia a comunidade conservacionista a desenvolver métodos rápidos para avaliações de riscos de extinção. Aqui, comparamos as avaliações da IUCN para 3.001 espécies de peixes dulcícolas neotropicais com dados facilmente acessíveis de risco de extinção: extensão de ocorrências, altitude e data de publicação das espécies. Além disso, usando apenas dados geográficos e taxonômicos, geramos avaliações preliminares de conservação para 2.334 espécies de peixes neotropicais aguardando avaliação da IUCN, e identificamos 671 espécies adicionais como potencialmente ameaçadas. Este número de espécies potencialmente ameaçadas representa um aumento de 59% em relação aquelas classificadas nas categorias de ameaça pela IUCN. Estes resultados expandem o número de espécies ameaçadas segundo a IUCN de 422 para 1.093 espécies ameaçadas ou potencialmente ameaçadas, representando cerca de 18% das espécies de peixes neotropicais. O risco de extinção é maior para espécies com distribuições geográficas restritas, que habitam rios de terras altas e que foram descritas mais recentemente. Sugerimos a região Central e Meridional do Andes e o Escudo das Guianas Orientais como prioridades para as próximas avaliações da IUCN sobre a conservação das espécies de peixes dulcícolas neotropicais.

Abstract The IUCN Red List (RL) provides high-quality conservation assessments for individual species, yet the rate and scale of environmental deterioration globally challenges the conservation community to develop expedited methods for risk assessment. Here we compare threat assessments for 3,001 species of Neotropical freshwater fishes (NFF) in the IUCN–RL using readily accessible data types as proxies for extinction risk: geographic range, elevation, and species publication date. Furthermore, using geographic and taxonomic data alone, we generated preliminary conservation assessments for 2,334 NFF species currently awaiting IUCN assessment, identifying an additional 671 NFF species as potentially threatened. This number of potentially threatened species represents an increase of 59% over the number of species currently assigned to threat categories by the IUCN–RL. These results substantially expand the number of threatened NFF species from 422 currently on the IUCN RL to 1,093 species as threatened or potentially threatened, representing about 18% of all NFF species. Extinction risk is greater in species with smaller geographic ranges, which inhabit upland rivers, and which were described more recently. We propose the Central and Southern Andes, and Eastern Guiana Shield as priorities in the upcoming IUCN RL assessment of NFF species conservation risk.

Abstract Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one of the genus Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae, Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper Paraguay system. Paracanthopoma saci is distinguished from its only congener, P. parva, by a spatulate caudal peduncle; a minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater Amazonian river systems (Amazon, Orinoco, Essequibo and smaller surrounding drainages). Their presence restricted to the Rio Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed using S-DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the Paraguay and Amazon drainages.

Resumo Uma espécie nova de Moenkhausia é descrita da drenagem do rio Machado, bacia Amazônica, Brasil. É diagnosticada das congêneres pelo padrão de coloração, que consiste na concentração de cromatóforos na porção anterior das escamas do corpo, em uma mancha horizontalmente alongada no pedúnculo caudal, na coloração dourada brilhante da porção dorsal do olho quando vivo e na faixa escura que atravessa o olho horizontalmente. A nova espécie apresenta variação na morfologia do canal da linha lateral do corpo. A maioria dos indivíduos totalmente desenvolvidos não possuem tubo ósseo fechado em muitas escamas da linha lateral, assemelhando-se aos estágios iniciais do desenvolvimento da formação do tubo de outras espécies. Essa condição pedomórfica é interpretada como resultado do truncamento do desenvolvimento. Tal processo evolutivo pode ter sido responsável pelos diferentes níveis de redução do canal sensorial de pequenos caracídeos. A variação neste caráter é comum, até entre os lados do mesmo indivíduo. Por isso, reafirmamos que o grau de desenvolvimento do canal sensorial do corpo deve ser usado com cuidado em estudos taxonômicos e filogenéticos, porque reduções no sistema látero-sensorial podem significar perdas paralelas em Characidae. Sugerimos que a espécie nova seja categorizada como Quase Ameaçada devido à distribuição geográfica restrita e ao declínio contínuo da qualidade do habitat.

Abstract A new species of Moenkhausia is described from the rio Machado drainage, Amazon basin, Brazil. It is diagnosed from congeners by its color pattern, consisting of the concentration of chromatophores on the anterior portion of body scales, the horizontally elongate blotch on caudal peduncle, a bright golden coloration of the dorsal portion of eye when alive, and a dark line crossing the eye horizontally. The new species has variable morphology regarding trunk lateral-line canals. Most fully grown individuals do not have enclosed bony tube in many lateral line scales, resembling early developmental stages of tube formation of other species. This paedomorphic condition is interpreted as a result of developmental truncation. Such evolutionary process may have been responsible for the presence of distinct levels of trunk lateral line reductions in small characids. Variation in this feature is common, even between the sides of the same individual. We reassert that the degree of trunk lateral-line tube development must be used with care in taxonomic and phylogenetic studies, because reductions in the laterosensory system may constitute parallel loss in the Characidae. We suggest the new species to be categorized Near Threatened due to the restricted geographical distribution and continuing decline in habitat quality.