Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context. Our recommendations are intended to spur discussion among biologists, as broad community consensus is critical ahead of the implementation of new editions of the International Code of Zoological Nomenclature and other Codes of bionomenclature.

Bilateral genital asymmetry in livebearer fishes of the genus Phalloceros Eigenmann, 1907, with description of a new species from coastal drainages of southern Brazil (Cyprinodontiformes: Poeciliidae).

A new species of Phalloceros is described from the Tijucas, Maruim, Aririú, Cubatão do Sul, Rio da Madre, D'Una and Tubarão river basins in southern Brazil. The new species is diagnosed among congeners by the bilateral asymmetry of a hood-like structure located immediately anterior to the urogenital papilla of females. The hood is fused with the urogenital papilla on the right side, but free from the papilla on the left side. This hood is reported for the first time in the genus and is present in six of the 21 valid species of Phalloceros, but its bilateral asymmetry is an exclusive condition of the new species. These species do not constitute a monophyletic group. The new species is likely to be phylogenetically related to P. caudimaculatus, whose females have a symmetrical hood.

Poor taxonomic sampling undermines nomenclatural stability: A reply to Roxo et al. (2019).

A recent study based on genomic data by Roxo et al. (2019) provided a phylogeny of the Loricariidae, the largest catfish family and second largest Neotropical fish family with approximately 1,000 species. The study represents a valuable and innovative contribution for understanding higher-level relationships within the family. The phylogenetic tree inferred by Roxo et al. (2019) thoroughly corroborates the monophyly and relationships of most currently accepted subfamilies of Loricariidae, based on a fair taxon sampling (nearly 14% of the species in the family) representing most genera of each but one of the subfamilies, the Lithogeninae, the sister-group of the remaining members of the family (Pereira & Reis, 2017; Reis et al., 2017). In addition to a hypothesis of relationships, Roxo et al. (2019) also proposed a series of lower-level taxonomic changes, which are deemed premature considering that the taxonomic sampling of the study targeted higher-level clades, and go against one of the pillars of biological classification: nomenclatural stability (e.g., Heterick & Majer, 2018; Beninger & Backeljau, 2019). Here we (1) discuss implications of inadequate taxonomic sampling as a basis for changes in classification of species; (2) explain why the taxonomic sampling design of Roxo et al. (2019) is inadequate for the proposed nomenclatural changes; and (3) advocate that changes to classifications must be grounded on phylogenies with dense sampling of taxa at the relevant level.

A new species of Bryconops (Ostariophysi: Characiformes: Characidae) from the upper rio Tocantins drainage, Brazil

A new species of the genus Bryconops , subgenus Bryconops , is described from the rio Conceição, a tributary to the rio Palma, upper rio Tocantins drainage, Tocantins State, Brazil. The new species is distinguished from all its congeners, except B. humeralis and B. vibex by the color pattern in vivo (dorsal, adipose, and caudal fins entirely orange). The new species is easily distinguished from B. humeralis and B. vibex by the absence of a humeral spot and by the lack of maxillary teeth (vs . presence of a single humeral spot and presence of 1-3 maxillary teeth on both sides). Furthermore, the new species is distinguished from B. vibex by the number of perforated lateral line scales (38-41 vs. 44-46).

Uma nova espécie do gênero Bryconops, subgênero Bryconops, é descrita do rio Conceição, um afluente do rio Palma, bacia do rio Tocantins, Estado do Tocantins, Brasil. A nova espécie distingue-se de suas congêneres, exceto B. humeralis e B. vibex pelo padrão de coloração in vivo (nadadeiras dorsal, adiposa e caudal inteiramente laranjas). A nova espécie distingue-se de B. humeralis e B. vibex pela ausência de mancha umeral e pela ausência de dentes maxilares (vs. presença de uma mancha umeral e presença de 1 a 3 dentes maxilares em ambos os lados). Além disso, a nova espécie distingue-se de B. vibex pelo número de escamas com poros na linha lateral (38-41 vs. 44-46).

Description of males of Phallotorynus pankalos Lucinda, Rosa & Reis, 2005 and reappraisal of Phallotorynus species relationships (Teleostei: Cyprinodontiformes: Poeciliidae)

Recently discovered male specimens of Phallotorynus pankalos are described and diagnosed from males of congener species on the basis of gonopodial morphology, color pattern and number of dorsal and anal-fin rays. The phylogenetic hypothesis of relationships among Phallotorynus species is reappraised with the inclusion of P. pankalos. Phallotorynus pankalos is hypothesized as sister to P. jucundus, a clade sister to P. victoriae or to a clade composed of P. dispilos and P. psittakos. Biogeography of Phallotorynus species is discussed, and it is suggested: (1) an early basal split between the rio Paraíba do Sul drainage and the Paraná-Paraguay system, separating P. fasciolatus from the ancestor of the remaining Phallotorynus species followed by a dispersal to rio Paraíba do Sul; (2) that the formation of the Sete Quedas falls may have isolated the ancestors of P. psittakos and P. dispilos. However, the sequence of events associated with the evolutionary history of Phallotorynus remains unclear and unsatisfactory.

Recentemente descobertos espécimes machos de Phallotorynus pankalos são descritos e diagnosticados dos machos de espécies congêneres com base na morfologia gonopodial, padrão de colorido e número de raios das nadadeiras dorsal e anal. A hipótese de relações filogenéticas entre as espécies de Phallotorynus foi reavaliada com a inclusão de P. pankalos. Phallotorynus pankalos é hipotetizado como irmão de P. jucundus, um clado irmão de P. victoriae ou a um clado composto por P. dispilos e P. psittakos. Biogeografia das espécies de Phallotorynus é discutida, e é sugerido: (1) uma separação basal entre as drenagens do rio Paraíba do Sul e o sistema Paraná-Paraguai, separando P. fasciolatus do ancestral dos demais Phallotorynus, seguida de uma dispersão para o rio Paraíba do Sul; (2) que a formação dos saltos das Sete Quedas podem ter isolado os ancestrais de P. psittakos e P. dispilos. No entanto, a sequência de eventos associados a história evolutiva de Phallotorynus continua obscura e insatisfatória.

A new species of the genus tetragonopterus cuvier, 1816 (ostariophysi: characiformes: characidae) from the rio Tocantins drainage, Brazil

A new species of the genus tetragonopterus is described from specimens of the upper and middle portions of the rio Tocantins drainage. the new species can be distinguished from all congeners by the possession of a very uniquely shaped maxilla.

Uma espécie nova do gênero tetragonopterus é descrita a partir de espécimes das porções superior e média da bacia do rio Tocantins. A espécie nova pode ser distinguida de todas as congêneres pela maxila de formato único.

Systematics and biogeography of the genus Phalloceros Eigenmann, 1907 (Cyprinodontiformes: Poeciliidae: Poeciliinae), with the description of twenty-one new species

The genus Phalloceros is revised. Phalloceros caudimaculatus (Hensel, 1868) and twenty-one new species are recognized in Phalloceros. The species and their distributions are: P. alessandrae, small coastal drainages of the Paraná State; P. anisophallos, small coastal drainages of the Rio de Janeiro State; P. aspilos, rio Parati-Mirim, Rio de Janeiro; P. buckupi, small coastal drainages of the Paraná State; P. caudimaculatus (Hensel, 1868), laguna dos Patos system, lower rio Uruguay, drainages of rio Tramandaí, rio Mampituba and coastal drainages of Uruguay and Argentina; P. elachistos, rio Doce drainage and small coastal drainages of the Espírito Santo State; P. enneaktinos, córrego da Toca do Boi, Rio de Janeiro; P. harpagos, rio Paraná-Paraguai basin and coastal drainages from Espírito Santo to Santa Catarina States; P. heptaktinos, rio Jacuí drainage; P. leptokeras, middle portions of rio Paraíba do Sul drainage; P. leticiae, upper rio Araguaia; P. lucenorum, rio Juquiá drainage; P. malabarbai, coastal drainage of the Santa Catarina State; P. megapolos, drainages of rio São João, rio Cubatão (North) and small adjacent drainages of the Paraná State; P. mikrommatos, rio João de Tiba basin, a coastal drainage of the Bahia State; P. ocellatus, coastal drainages of the Bahia and Espírito Santo States; P. pellos, small coastal drainages of the Paraná State; P. reisi, headwaters of rio Tietê, rio Paraíba do Sul, rio Ribeira de Iguape, and small coastal drainages of the São Paulo State; P. spiloura, coastal drainages of the Rio Grande do Sul and Santa Catarina States; P. titthos, coastal drainages of the Paraná State; P. tupinamba, rio Itamambuca and rio Macacu drainages, small coastal drainages of the São Paulo and Rio de Janeiro States, and P. uai, rio São Francisco basin. A lectotype for Girardinus caudimaculatus is designated. Diagnoses of intrageneric clades of Phalloceros are provided. Diagnoses and descriptions of distributions are provided...

O gênero Phalloceros é revisado. Phalloceros caudimaculatus (Hensel, 1868) e vinte e uma espécies novas são reconhecidas em Phalloceros. As espécies e suas distribuições são: P. alessandrae, pequenas bacias costeiras do Estado do Paraná; P. anisophallos, pequenas bacias costeiras do Estado do Rio de Janeiro; P. aspilos, rio Parati-Mirim, Rio de Janeiro; P. buckupi, pequenas bacias costeiras do Estado do Paraná; P. caudimaculatus (Hensel, 1868), sistema da Laguna dos Patos, baixo rio Uruguai, bacias dos rios Tramandaí, Mampituba e drenagens costeiras do Uruguai e Argentina; P. elachistos, drenagem do rio Doce e pequenas bacias costeiras do Estado do Espírito Santo; P. enneaktinos, córrego da Toca do Boi, Rio de Janeiro; P. harpagos, bacia do rio Paraná-Paraguai e bacias costeiras do Espírito Santo a Santa Catarina; P. heptaktinos, bacia do rio Jacuí; P. leptokeras, porção média da bacia do rio Paraíba do Sul; P. leticiae, porção superior do rio Araguaia; P. lucenorum, drenagem do rio Juquiá; P. malabarbai, drenagem costeira do Estado de Santa Catarina; P. megapolos, drenagens dos rios São João, rio Cubatão (Norte) e pequenas drenagens adjacentes no Estado do Paraná; P. mikrommatos, bacia do rio João de Tiba, drenagem costeira do Estado da Bahia; P. ocellatus, drenagens costeiras dos Estados da Bahia e Espírito Santo; P. pellos, pequenas bacias costeiras do Estado do Paraná; P. reisi, cabeceiras do rio Tietê, rio Paraíba do Sul, rio Ribeira de Iguape, e pequenas bacias costeiras do Estado de São Paulo; P. spiloura, bacias costeiras dos Estados do Rio Grande do Sul e Santa Catarina; P. titthos, bacias costeiras do Estado do Paraná; P. tupinamba, bacias dos rios Itamambuca e Macacu, pequenas drenagens costeiras dos Estados de São Paulo e Rio de Janeiro e P. uai, bacia do rio São Francisco. Um lectótipo para Girardinus caudimaculatus Hensel, 1868 é designado. São apresentadas diagnoses dos clados intragenéricos de Phalloceros. Diagnoses e...

Three new Pimelodus species (Siluriformes: Pimelodidae) from the rio Tocantins drainage, Brazil

Three new species of Siluriformes from the rio Tocantins drainage of Brazil are placed in the genus Pimelodus, P. stewarti, P. joannis, and P. halisodous. Pimelodus halisodous differs from the sympatric P. joannis and P. stewarti by the number of premaxillary tooth rows (13-16 vs. 5-9). Pimelodus joannis differs from P. stewarti by the presence of two dark blotches on the base of the caudal fin. The three new species differ from all other species of Pimelodus by the possession of a uniform gray coloration along flanks; the relatively short distance between the posterior nostril and the anterior orbital border; a short maxillary barbel, that only slightly surpasses the caudal-fin base.

Três espécies novas de Siluriformes da bacia do rio Tocantins são alocadas no gênero Pimelodus: P. stewarti, P. joannis e P. halisodous. Pimelodus halisodous difere das espécies simpátricas P. joannis e P. stewarti pelo número de fileiras de dentes do pré-maxilar (13-16 vs. 5-9). Pimelodus joannis difere de P. stewarti pela presença de duas manchas negras na base na nadadeira caudal. As três novas espécies diferem das demais espécies de Pimelodus pela coloração cinza uniforme ao longo dos flancos; curta distância entre a narina posterior e a margem anterior da orbita; e barbilhões maxilares curtos, ultrapassando levemente a base da nadadeira caudal.