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(Received 7 July 2021; accepted 23 September 2021) Two new characid fish species are described from the upper rio Tocantins basin, Chapada dos Veadeiros, Goiás State, Brazil. Both species were discovered among specimens in museum collections. Relationships of taxa were evaluated in a more comprehensive phylogenetic analysis utilizing the largest dataset available of molecular and morphological data for the family Characidae. The two species were recovered as sister species and described in a new genus, closely related to Erythrocharax and Phycocharax. Dinotopterygium gen. nov. is distinguished from all other characid genera by the unique combination of ten synapomorphies, including the unique anal-fin morphology with a small number of branched anal-fin rays (13-16). Dinotopterygium uniodon sp. nov. and D. diodon sp. nov. differ by the number of tooth series in the premaxillary bone (one or two) and number of tooth cusps (7 or 5). The additional phenotypic variation for a taxonomically informative character within the Characidae through the discovery of new forms has helped to refine the interrelationship of the tribe Probolodini (Characidae: Stethaprioninae). The discovery of these new and possibly critically endangered species emphasizes the importance of museum collections for understanding biodiversity past and present. [ABSTRACT FROM AUTHOR]

Arapaima gigas (Schinz), the "pirarucu", is one of largest freshwater fish of the Neotropical region, naturally occurring in the Amazon, Essequibo, and Orinoco river basins. Herein, it is first recorded from the Grande River, in the upper Paraná River basin. This record is based on the finding of one dead specimen on the left margin of the Grande River, and in situ observation of juveniles and adults in the river. [ABSTRACT FROM AUTHOR]

Hyphessobrycon langeanii was originally described as endemic to the upper Araguaia river basin, Brazil. However, our analysis of several Hyphessobrycon specimens collected in the Correntes river basin and another tributary of the Itiquira River in Mato Grosso state (both belonging to the Paraguay river basin) reveals the first verified record of H. langeanii from this basin and from the states of Mato Grosso do Sul and Mato Grosso. The objective of this study is to provide a novel record of H. langeanii from the basin of the Paraguay River and from the state of Mato Grosso do Sul. We compare the newly discovered populations with the populations in the Araguaia river basin, and we also provide a brief discussion on the biogeography of this species. [ABSTRACT FROM AUTHOR]

Hypostomus khimaera Tencatt, Zawadzki & Fröehlich, 2014 is a species native to the rio Paraguay basin, but it is recorded here from the upper rio Paraná basin for the first time. Our new record was made in the córrego Mimoso, a tributary of the rio Anhanduí, approximately 180 km from the closest previously reported locality. We are unsure whether the occurrence of this species in the upper rio Paraná basin is a consequence of natural phenomena, such as headwater connection during floods or stream capture, or an artificial introduction. Together with the invasive H. cochliodon Kner, 1854, H. khimaera is the second species of the H. cochliodon group recorded in the upper rio Paraná basin. Here, we provide an updated diagnosis of H. khimaera and highlight the differences in opercle exposition as the easiest way to differentiate it from the syntopic and morphologically similar H. cochliodon. [ABSTRACT FROM AUTHOR]

Ectrepopterus uruguayensis Fowler was recently redescribed, with occurrence in lower tributaries of Río de la Plata and lower Río Uruguay, Uruguay. Herein its occurrence is extended and confirmed to Argentina, arroyo El Molino, in Uruguay Department, Entre Ríos Province, Uruguay drainage. [ABSTRACT FROM AUTHOR]

The upper rio Paraná basin drains the most developed and environmentally degraded region in South America: the Brazilian southeast. While it is one of the most well-known Neotropical fish assemblages, it is also one of the most threatened by anthropic activity. Urbanization, deforestation, dam construction, invasive species, and water pollution not only reduce the living area of species but also alter our perception of the basin and its biotic elements. Such changes are so profound and pervasive that raise uncertainties about the native or non-native status of several species. This paper aims to offer a detailed picture of the native diversity and historical biogeography of the fishes in the upper rio Paraná basin, which we hope will offer a solid foundation for future conservation policies. We update the list of native species, analyze geographical distributions, and identify biogeographical patterns, emphasizing areas requiring recognition as distinct biotas for conservation efforts. Over the past 15 years, more than 100 additional species have been described or recorded, expanding the total to 341 native species belonging to six orders and 30 families, making it the richest river basin in Brazil outside the Amazonian region. Unlike most neotropical basins where Characidae dominates, loricariids make up nearly one-fourth of the total fish diversity in the region. Species and clades concentrate in the central basin, while endemics are confined to peripheral areas due to the complex biogeographical history shared with neighboring basins. Eighteen distinct biogeographical regions are identified, discussing their composition, histories, and conservation implications. The upper rio Paraná basin has 10% of its fish fauna ranked as endangered and present 128 non-native species, including three hybrids. This places it as the major drainage with the largest number of endangered taxa in the neotropics and at the same time the one with the most numerous non-native elements. Existing protected areas are deemed ineffective in preserving diverse assemblages and fail to safeguard the majority of threatened and narrowly-endemic species. [ABSTRACT FROM AUTHOR]

A checklist of recent and fossil fishes of the Order Characiformes is presented herein and believed to be complete through 2022. A total of 47 collaborators checked and provided information about their taxa of expertise. The list is arranged in alphabetical order by family and then genus and includes all available synonyms. From a total of 3,087 species group names and 527 genus group names, 2,334 species are currently treated as valid, and assigned to 301 genera and 24 families. This total includes 25 species known only from the fossil record, of which 21 are assigned to eight extant families and four are Incertae sedis in Characiformes, but does not include five species based on fossil which were wrongly treated in Characiformes. The status of 79 nominal species remains unresolved. When there are two competing hypotheses about the validity of a name, one of them is chosen and the alternate interpretation is provided in the remark section of that name. Distributional summaries are presented as numbers that correspond to areas for which there is a record of occurrence of the species. A list of unavailable names is provided at the end since some of those names may need additional research to certify their status. [ABSTRACT FROM AUTHOR]

Among Neotropical freshwater ecoregions, the Mid-Northeastern Caatinga (MNCE) is a fish knowledge gap. Its temporary drainages are receptors of the São Francisco interbasin water transfer project (SFR-IWT) in the Brazilian semiarid. We provide a comprehensive baseline of fish richness of the five SFR-IWT basins. Species richness, shared, endemic, threatened and non-native species were obtained using sampling, ichthyologic collections, literature and online repositories (306 localities). In total 121, species were recorded, 111 of them native, and 16 (14.41%) listed for all basins. Higher richness of native species (78, 70.27%) was recorded in the São Francisco lowermiddle stretch (SFRE), including 23 endemic, 61 (54.95%) in MNCE basins (13 endemic), and 28 (25.23%) shared between both ecoregions. In the MNCE, 50 species were recorded in Jaguaribe (JAG), 39 in Piranhas-Açu, 36 in Paraíba do Norte, and 32 in Apodi-Mossoró (APO). The number of species shared between the SFRE and each receptor basin varied from 24 (23.08%, JAG) to 20 (22.22%, APO). JAG contains 81.97% of the receptor basins' species. Its higher richness and endemism deserve special attention regarding the ongoing hydrological changes. This study will help detect possible modifications in the ichthyofauna of the main MNCE drainages. [ABSTRACT FROM AUTHOR]

Hyphessobrycon itaparicensis was originally described from a small stream in the Itaparica coastal island, Bahia State, Brazil, and has been sampled in several coastal rivers draining Bahia and Sergipe States. Broad examination of type material and recently collected specimens resulted in the redescription provided herein. The presence of one humeral blotch, absence of pseudotympanum, and conservation aspects of H. itaparicensis are briefly discussed. Data obtained from the original description, paratypes and topotypes of H. sergipanus showed broad overlap with H. itaparicensis and absence of morphological diagnostic features supporting the recognition of H. sergipanus as a valid species. Thus, H. sergipanus is considered as junior synonym of H. itaparicensis. We emphasize the need of examining large population samples and type material of similar congeners to avoid improper propositions of new specific names. [ABSTRACT FROM AUTHOR]

Neotropical Ichthyology promotes the Special Issue (SI) “Human impacts and the loss of Neotropical freshwater fish diversity” with the purpose of publishing relevant scientific articles on the current biodiversity crisis and the loss of Neotropical freshwater fishes in the Anthropocene. The SI is composed of 22 publications, being two review articles and 20 original articles. A total of 107 researchers contributed to these papers, involving 44 institutions based in Brazil and six other countries. Published articles investigated main anthropic activities and their impacts on fish diversity, with special focus on river regulation, mining, land use changes, aquaculture, and fisheries. Studies provided evidence about the loss of fish diversity in the Neotropics, including fish kill events, demographic changes, contamination, changes in assemblage structure, loss of taxonomic and functional diversity, besides the degradation of ecosystem functions and services, and the lack of effective protection and conservation. Studies were conducted in rivers, streams, lakes, and reservoirs from different Neotropical systems. The studies published in this SI represent a relevant sample of the current worrisome situation of freshwater fishes in the Neotropical region and call for urgent revision in environmental policies, management and conservation initiatives, and socioeconomic priorities. [ABSTRACT FROM AUTHOR]