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Amphipods in the parvorder Hadziidira are typically associated with algae, sponges, or coral rubble. Members of the parvorder have a gnathopod 2 that is stouter than gnathopod 1, a pair of dorsal robust setae on urosomite 2, and a basofacial robust seta on the uropod 1 peduncle. Within the parvorder, six families are documented from Bocas del Toro, Panama, represented by 26 species. This research documents range extensions for all 26 species and an identification key to the species of Caribbean Hadziidira of Panama is provided.

ResumenLos anfípodos del parvorden Hadziidira suelen estar asociados con algas, esponjas o escombros de coral. Los miembros del parvorden tienen un gnatópodo 2 que es más robusto que el gnatópodo 1, un par de setas dorsales robustas en el urosomita 2 y una seta basofacial robusta en el pedúnculo del urópodo 1. Dentro del parvorden se documentan seis familias de Bocas del Toro, Panamá, representadas por 26 especies. Esta investigación documenta extensiones de rango para las 26 especies y se proporciona una clave de identificación para las especies de Hadziidira caribeña de Panamá.

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The ants of the genus Rhopalothrix are diverse in the Neotropical region, with 14 of the 16 described species. Based on museum material and recent fieldwork, Rhopalothrix ants in Colombia were reviewed. Morphological analysis of the workers allowed delimitation of six species, including two new species, Rhopalothrixmandibularis Guerrero & Grajales, sp. nov. and Rhopalothrixmariaemirae Tocora, Fiorentino & Fernández, sp. nov. A new combination Rhopalothrixamaticomb. nov. is proposed for Eurhopalothrixamati. A worker-based taxonomic key, high-definition images of the workers, and a distribution map of all Rhopalothrix species present in Colombia are provided.

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The Neotropical planthopper genus Trigava O'Brien, 1999 (Hemiptera, Fulgoromorpha, Dictyopharidae, Nersiini) is revised. Four species are included: T.brachycephala (Melichar, 1912) (the type species, from Peru), T.obrieni Song, Malenovský & Deckert, sp. nov. (from Brazil), T.peruensis Song, O'Brien & Bartlett, sp. nov. (from Peru), and T.recurva (Melichar, 1912) (from Bolivia and Peru). Lectotypes are designated for Igavabrachycephala Melichar, 1912 and Igavarecurva Melichar, 1912. All species are described, including habitus photographs and detailed illustrations of the male genitalia. Male and female genitalia are described for this genus for the first time. A key for identification of the species of Trigava and a distribution map are provided.

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The genus Uaiuara rheims is revisited. A new species is described, based on females from Iquitos, Peru and new distribution records for Uaiuara amazonica (Simon, 1880) and U. quyguaba rheims, 2013 are provided. In addition, an identification key and updated distribution maps are provided for all species.

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Background: Identifying species, particularly small metazoans, remains a daunting challenge and the phylum Nematoda is no exception. Typically, nematode species are differentiated based on morphometry and the presence or absence of certain characters. However, recent advances in artificial intelligence, particularly machine learning (ML) algorithms, offer promising solutions for automating species identification, mostly in taxonomically complex groups. By training ML models with extensive datasets of accurately identified specimens, the models can learn to recognize patterns in nematodes' morphological and morphometric features. This enables them to make precise identifications of newly encountered individuals. Implementing ML algorithms can improve the speed and accuracy of species identification and allow researchers to efficiently process vast amounts of data. Furthermore, it empowers non-taxonomists to make reliable identifications. The objective of this study is to evaluate the performance of ML algorithms in identifying species of free-living marine nematodes, focusing on two well-known genera: Acantholaimus Allgén, 1933 and Sabatieria Rouville, 1903. Methods: A total of 40 species of Acantholaimus and 60 species of Sabatieria were considered. The measurements and identifications were obtained from the original publications of species for both genera, this compilation included information regarding the presence or absence of specific characters, as well as morphometric data. To assess the performance of the species identification four ML algorithms were employed: Random Forest (RF), Stochastic Gradient Boosting (SGBoost), Support Vector Machine (SVM) with both linear and radial kernels, and K-nearest neighbor (KNN) algorithms. Results: For both genera, the random forest (RF) algorithm demonstrated the highest accuracy in correctly classifying specimens into their respective species, achieving an accuracy rate of 93% for Acantholaimus and 100% for Sabatieria, only a single individual from Acantholaimus of the test data was misclassified. Conclusion: These results highlight the overall effectiveness of ML algorithms in species identification. Moreover, it demonstrates that the identification of marine nematodes can be automated, optimizing biodiversity and ecological studies, as well as turning species identification more accessible, efficient, and scalable. Ultimately it will contribute to our understanding and conservation of biodiversity.

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Amphipods in the parvorder Oedicerotidira are burrowers, furrowers, or surface skimmers. Members of the parvorder share a well-developed posteroventral lobe on coxa 4, an equilobate coxa 5, an immensely elongate pereopod 7 that differs in structure from pereopod 6, and an entire telson. Within the parvorder, only the family Oedicerotidae has been documented from Bocas del Toro, Panama, represented by two species. This research documents a range extension for Hartmanodesnyei (Shoemaker, 1933) and describes a new species of Synchelidium Sars, 1892. An identification key to the species of Caribbean Oedicerotidae of Panama is provided.

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Two new species of Bujurquina are described from the Bolivian Amazon basin. The first new species inhabits the Beni River drainage and is distinguished from its congeners in the combination of the following characters: longer snout, deeper head, body and caudal peduncle, shorter pectoral fin, more scales in the E1 series, discontinuous longitudinal band, bars 5 and 6 not fused, preopercular spot and coloration pattern on flank scales absent. The second new species inhabits the Mamoré and Iténez river drainages, and differs from its congeners in the combination of the following characteristics: longer and deeper head, longer snout and pectoral fin, deeper caudal peduncle, fewer scales in the E1 series and lower lateral line, preopercular spot absent, bars 6 and 7 separated from longitudinal band and discontinuous longitudinal band. An identification key for species reported from Bolivia and complementary morphological data for B. oenolaemus and B. vittata are presented.

Se describen dos especies nuevas de Bujurquina para la cuenca Amazónica de Bolivia. La primera nueva especie habita la cuenca del Río Beni y se distingue de sus congéneres en la combinación de los siguientes caracteres: hocico más largo, cabeza, cuerpo y pedúnculo caudal más bajos, aleta pectoral más corta, mayor número de escamas en la serie E1, banda longitudinal discontinua, barras 5 y 6 no fusionadas, mancha preopercular y patrón de coloración en las escamas de los flancos ausentes. La segunda nueva especie habita las cuencas de los ríos Mamoré e Iténez, y se diferencia de sus congéneres en la combinación de las siguientes características: cabeza más larga y alta, hocico y aleta pectoral más largos, pedúnculo caudal más alto, menor número de escamas de la serie E1 y de la línea lateral inferior, ausencia de la mancha preopercular, barras 6 y 7 separadas de la banda longitudinal y banda longitudinal discontinua. Se presenta una clave de identificación de las especies de Bolivia y datos morfológicos complementarios de B. oenolaemus y B. vittata.

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The early ontogeny of Triportheus albus and T. angulatus, two fish species of Triportheidae, is described using morphological, meristic, and morphometric characters. These species are exploited by subsistence fisheries and have potential as an alternative source of fish, given the decline in the natural stocks of other commercially important fish species in the Amazon. The specimens were collected in the open water limnetic zone, under of the macrophyte stands, and in subsurface areas near sandbars in the Amazon basin. Intra and interspecific morphometric analyzes were performed to evaluate growth models between species. The combination of color pattern, body morphology, morphometric proportions and myomeres number distinguishes the species from each other and from other congeners. Some morphometric relationships related to head as snout length and eye diameter as well as length from the snout to the origins of anal and length from the snout to the origins of pelvic, related with standard length were different between the two species of Triportheus, reflecting different growth models between them. An identification key for larvae and juveniles of some species of Triportheus from the Eastern Amazon is presented.(AU)

A ontogenia inicial de Triportheus albus e T. angulatus, duas espécies de peixes pertencentes a Triportheidae, é descrita usando caracteres morfológicos, merísticos e morfométricos. Essas espécies são exploradas pela pesca de subsistência e têm potencial como fonte alternativa de pescado, dado o declínio nos estoques naturais de outras espécies de peixes comercialmente importantes na Amazônia. Os espécimes foram coletados na zona limnética de águas abertas, sob bancos de macrófitas e em áreas subsuperficiais próximas a bancos de areia na bacia amazônica. Análises morfométricas, intra e interespecíficas, foram realizadas para avaliar modelos de crescimento entre as espécies. A combinação do padrão de coloração, morfologia corporal, proporções morfométricas e número de miômeros distingue as espécies entre si e de outras congêneres. Algumas relações morfométricas relacionadas à cabeça, como comprimento do focinho e diâmetro do olho, assim como o comprimento do focinho à origem da nadadeira anal e o comprimento do focinho à origem da nadadeira pélvica, relacionadas ao comprimento padrão foram diferentes entre as duas espécies de Triportheus, refletindo modelos distintos de crescimento entre elas. Uma chave de identificação para larvas e juvenis de algumas espécies de Triportheus da Amazônia Oriental é apresentada.(AU)

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The Educator Group of the Melanoconion Section of Culex (Melanoconion) (Diptera, Culicidae) is reviewed. Currently, the group includes the following valid species: Culex (Melanoconion) aphyllusTalaga, 2020, Culex (Melanoconion) cristovaoi Duret, 1968, Culex (Melanoconion) educatorDyar & Knab, 1906, Culex (Melanoconion) eknomiosForattini & Sallum, 1992, Culex (Melanoconion) inadmirabilisDyar, 1928, Culex (Melanoconion) rachoui Duret, 1968, Culex (Melanoconion) theobaldi (Lutz), 1904, Culex (Melanoconion) vaxusDyar, 1920, Culex (Melanoconion) angularis Sá & Sallum n. sp., Culex (Melanoconion) spiniformis Sá & Hutchings n. sp., Culex (Melanoconion) longistriatus Sá & Hutchings n. sp., Culex (Melanoconion) anelesDyar & Ludlow, 1922, Culex (Melanoconion) apeteticus Howard, Dyar & Ludlow, 1913, and Culex (Melanoconion) bibulusDyar, 1920. The last three species were resurrected from synonymy of either Cx. educator or Cx. vaxus. Descriptions, differential diagnoses, bionomics, and geographical data are provided for each species when available.

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The Nearctic species of Saropogon Loew, 1847 north of Mexico are reviewed, with 19 species recognized and one described as new: Saropogonpyrodes sp. nov. from Arizona. This previously recognized new species has awaited description since its first collection in 1964. Only after a community scientist posted photographs taken in nature to an online database did its description become a priority. All species of Saropogon occurring in the Nearctic Region north of the Mexican border have been reexamined. Photographs and diagnoses of all species are provided with a distribution map of the included specimens studied. An updated key to the Nearctic species north of Mexico is provided. Finally, the need for a review of the diverse Mexican fauna is expressed.

RESUMO

In this paper, I revisit the genus Extraordinarius Rheims. I describe the female of E. klausmeinei Rheims and two new species: E. alicecooperispec. nov. (♂♀) from Espírito Santo and E. angusyoungispec. nov. (♀) from Rio de Janeiro, all in southeastern Brazil. In addition, I include an identification key for all species of the genus, a new record for E. brucedickinsoni Rheims and an updated distribution map for the genus.

RESUMO

A new genus of Hypopopomatinae armored catfish is described from the northern portions of South America, namely the Amazon, Orinoco and Guianan coastal drainages. The new genus is diagnosed from all remaining hypoptopomatines by having the canal cheek plate on the ventral surface of the head posteriorly elongated and contacting the cleithrum, in addition to other features that distinguish the new genus from specific genera. Five new species are described and 18 species currently allocated in Parotocinclus, Hisonotus, and Curculionichthys are transferred to the new genus and rediagnosed. Parotocinclus amazonensis and P. aripuanensis are considered junior synonyms of P. britskii. The secondary sexual dimorphism of the members of the new genus is detailed and illustrated. Morphological characters are used to delimit four phenotypic groups of species that might have phylogenetic significance, which still have to be properly tested. A key to the species is offered and diagnoses, illustrations, and distribution maps are provided for all species.(AU)

Um novo gênero de cascudo da subfamília Hypopopomatinae é descrito das porções do norte da América do Sul, a saber, as drenagens costeiras da Amazônia, Orinoco e Guiana. O novo gênero é diagnosticado de todos os demais hypoptopomatineos por possuir a placa com canal da bochecha na superfície ventral da cabeça, alongada posteriormente e em contato com o cleitro, além de outras características que distinguem o novo gênero de gêneros específicos. Cinco novas espécies são descritas e 18 espécies atualmente alocadas em Parotocinclus, Hisonotus e Curculionichthys são transferidas para o novo gênero e rediagnosticadas. Parotocinclus amazonensis e P. aripuanensis são considerados sinônimos juniores de P. britskii. O dimorfismo sexual secundário dos membros do novo gênero é detalhado e ilustrado. Caracteres morfológicos são usados para delimitar quatro grupos fenotípicos de espécies que podem ter significado filogenético, que ainda precisam ser devidamente testados. Uma chave para as espécies é apresentada e diagnoses, ilustrações e mapas de distribuição são fornecidos para todas as espécies.(AU)

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Aspidoras comprises 25 species currently considered as valid, being widely distributed in Brazil, occurring from the upper rio Paraná basin in São Paulo to coastal basins of Ceará. After Nijssen, Isbrücker's review more than 40 years ago, no extensive work regarding the taxonomy of Aspidoras was conducted. Our paper presents a comprehensive taxonomic revision of the genus, based primarily on the extensive material that has been collected since then. Considering the new diagnosis plus the available phylogenetic data, A. pauciradiatus and A. virgulatus are transferred to Corydoras and Scleromystax, respectively. New synonymies are proposed: A. eurycephalus and A. taurus with A. albater; A. menezesi and A. spilotus with A. raimundi; and A. microgalaeus and A. marianae with A. poecilus. Additionally, a new species from the Araguaia and Paraguay river basins is described, which can be distinguished from its congeners by the morphology of its complex vertebra and infraorbital 1. Thereby, the number of valid species within Aspidoras was reduced from 25 to 18. Redescriptions for A. albater, A. belenos, A. depinnai, A. fuscoguttatus, A. lakoi, A. maculosus, A. poecilus, A. psammatides, A. raimundi, and A. velites are provided. An identification key to the species of Aspidoras is also provided.

Aspidoras compreende 25 espécies atualmente consideradas como válidas, sendo amplamente distribuído no Brasil, ocorrendo desde a bacia do alto rio Paraná em São Paulo até as bacias costeiras do Ceará. Após a revisão de Nijssen, Isbrücker há mais de 40 anos, nenhum trabalho extensivo sobre a taxonomia de Aspidoras foi conduzido. Nosso trabalho apresenta uma revisão taxonômica abrangente do gênero, baseada principalmente no extenso material que foi coletado desde então. Considerando a nova diagnose mais os dados filogenéticos disponíveis, A. pauciradiatus e A. virgulatus são transferidas para Corydoras e Scleromystax, respectivamente. Novas sinonímias são propostas: A. eurycephalus e A. taurus com A. albater; A. menezesi e A. spilotus com A. raimundi; e A. microgalaeus e A. marianae com A. poecilus. Adicionalmente, uma espécie nova é descrita das bacias dos rios Araguaia e Paraguai, podendo ser distinguida de suas congêneres pela morfologia da vértebra complexa e infraorbital 1. Assim, o número de espécies válidas em Aspidoras foi reduzido de 25 para 18. Redescrições para A. albater, A. belenos, A. depinnai, A. fuscoguttatus, A. lakoi, A. maculosus, A. poecilus, A. psammatides, A. raimundi e A. velites são fornecidas. Uma chave de identificação para as espécies de Aspidoras também é fornecida.

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The genus Harttia belongs to the subfamily Loricariinae and has to date 27 described species, distributed in the drainages of Guiana Shield, Amazon and southeastern Brazil. The new species is distinguished from its congeners by the combination of: canal plate present; abdominal plates absent; trapezoid preanal plates; males with elongated and conspicuous odontodes on the first pectoral-fin ray and on the lateral region of the head, close to the canal plate; and dorsal-fin spinelet present. An identification key for the species of the rio São Francisco basin and a comparison between the new taxon and all other species of the genus are presented.

O gênero Harttia pertence à subfamília Loricariinae e possui 27 espécies descritas, distribuídas nas drenagens do Escudo das Guianas, Amazônica e do sudeste brasileiro. A nova espécie distingue-se das congêneres pela combinação de: placa do canal presente; placas abdominais ausentes; placas pré-anais trapezóides; machos com odontódeos alongados e conspícuos no primeiro raio da nadadeira peitoral e na região lateral da cabeça, próximo a placa do canal; e spinelet da nadadeira dorsal presente. Apresenta-se uma chave de identificação para as espécies da bacia do rio São Francisco e a comparação com todas as demais espécies do gênero.

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We described the early development of Myloplus asterias and M. lobatus, two fish species of the Serrasalmidae using morphological, meristic, and morphometric characteristics. These herbivores serrasalmids are heavily fished because of their commercial importance in the Amazon. The individuals were collected between 2016 and 2020 in the limnetic zone of open water and macrophyte stands in the Lower Amazon River floodplain. We tested different growth models to identify the development pattern of these species. During the initial ontogeny, these two species can be differentiated mainly by the myomeres total number, 37 to 39 in M. asterias vs. 40 to 41 in M. lobatus, the pigmentation pattern, and dorsal-fin ray numbers. These characteristics are effective in distinguishing these species from other serrasalmids. The morphometric relationships were also different between these two species, showing distinct patterns in growth between the analyzed features. An identification key for larvae of some sympatric Serrasalmidae species from the Amazon basin is presented. Our expectation is that this study will contribute to the knowledge of the initial ontogeny and the biology of fish species in the Neotropical region.(AU)

Descrevemos o desenvolvimento inicial de Myloplus asterias e M. lobatus, duas espécies de peixes da família Serrasalmidae usando características morfológicas, merísticas e morfométricas. Esses serrasalmídeos herbívoros são fortemente pescados devido à sua importância comercial na Amazônia. Os indivíduos foram coletados entre 2016 e 2020 na zona limnética de águas abertas e em bancos de macrófitas na planície de inundação do baixo rio Amazonas. Testamos diferentes modelos de crescimento para identificar o padrão de desenvolvimento dessas espécies. Durante a ontogenia inicial, essas duas espécies podem ser diferenciadas pelo número total de miômeros; 37 a 39 em M. asterias vs. 40 a 41 em M. lobatus; pelo padrão de pigmentação e número de raios da nadadeira dorsal. Essas características são eficazes para distinguir essas espécies de outros serrasalmídeos. As relações morfométricas também foram diferentes entre as duas espécies, com distintos padrões de crescimento entre as características analisadas. Uma chave de identificação para larvas de algumas espécies simpátricas de Serrasalmidae da bacia amazônica é apresentada. Nossa expectativa é que este estudo contribua para o conhecimento da ontogenia inicial e da biologia das espécies de peixes da região Neotropical.(AU)

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Herein we describe two new species of Diapoma, one from the Negro River, a tributary of the Uruguay River in Brazil and Uruguay, and one from the Iguaçu River, in Brazil and Argentina. The new species from the Negro River basin is distinguished from its congeners by the following combination of characters: a black narrow and conspicuous line restricted to the body horizontal septum, incomplete lateral line, tricuspid teeth in the inner series of the premaxilla, and a lower body depth at vertical through the dorsal-fin origin (29.3-32.8% SL in males and 27.7-33.3% SL in females). The new species from the Iguaçu River basin is distinguished from its congeners by the following combination of characters: a discontinuous lateral line, adipose fin hyaline, longer anal-fin base (26.5-32.4% SL), and a longitudinal black stripe along the median region of caudal-fin rays. Additionally, we updated the molecular phylogeny of the genus, including new sequences from these two new species and Diapoma thauma. An identification key for species of Diapoma is presented, modified from previous study.(AU)

Neste trabalho descrevemos duas espécies novas de Diapoma, uma do rio Negro, afluente do rio Uruguai, Brasil e Uruguai, e a segunda do rio Iguaçu, Brasil e Argentina. A espécie nova do rio Negro é diagnosticada de suas congêneres pela combinação das seguintes características: uma linha preta, estreita e conspícua restrita ao septo horizontal do corpo, linha lateral incompleta, dentes da série interna da pré-maxila tricuspidados, e baixa altura do corpo na vertical que passa pela origem da nadadeira dorsal (29,3-32,8% SL em machos e 27,7-33,3% SL em fêmeas). A espécie nova do rio Iguaçu é diagnosticada de suas congêneres pela combinação das seguintes características: linha lateral descontínua, nadadeira adiposa não pigmentada de preto, base da nadadeira anal longa (26,5-32,4% SL) e raios médios da nadadeira caudal com uma linha preta longitudinal. Adicionalmente, atualizamos a filogenia molecular do gênero, incluindo novas sequências destas duas espécies novas e de Diapoma thauma. Uma chave de identificação para as espécies de Diapoma é apresentada, modificada de estudo anterior.(AU)

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Three new species of Eigenmannia belonging to the E. trilineata species-group are described. The first species is described from rio Mearim basin and can be diagnosed by lateral line stripe restricted to last two thirds of body, superior midlateral stripe present, 176-205 anal-fin rays, 10-15 scales rows above lateral line, 109-125 lateral line scales, 19-23 premaxillary teeth, 20-29 dentary teeth, 6-10 endopterygoid teeth, and 13-14 precaudal vertebrae. The second species is described from upper rio Parnaíba, and can be diagnosed by lateral line stripe restricted to last two-thirds of body, ii,11-13 pectoral-fin rays, 180-196 anal-fin rays, 12-15 scales rows above lateral line, 10-14 premaxillary teeth, 15-21 dentary teeth, 8-10 endopterygoid teeth, and 14 precaudal vertebrae. The third species is widespread in rio Parnaíba basin, and can be diagnosed by absence of lateral line stripe, absence of superior midlateral stripe, 182-228 anal-fin rays, 12-15 scales rows above lateral line, 107-131 lateral line scales, 32-34 premaxillary teeth, 35-44 dentary teeth, 9-12 endopterygoid teeth, and 13 precaudal vertebrae. A dichotomous key and the conservation status for the three species are provided.(AU)

Três espécies novas de Eigenmannia pertencentes ao grupo E. trilineata são descritas. A primeira espécie é descrita para a bacia do rio Mearim e pode ser diagnosticada por apresentar faixa da linha lateral restrita aos últimos dois terços do corpo, faixa médio lateral superior presente, 176-205 raios na nadadeira anal, 10-15 fileiras de escamas acima da linha lateral, 109-125 escamas na linha lateral, 19-23 dentes pré-maxilares, 20-29 dentes no dentário, 6-10 dentes no endopterigóide, e 13-14 vértebras pré-caudais. A segunda espécie é descrita do alto rio Parnaíba, e pode ser diagnosticada por apresentar faixa da linha lateral restrita aos últimos dois terços do corpo, ii,11-13 raios na nadadeira peitoral, 180-196 raios na nadadeira anal, 12-15 fileiras de escamas acima da linha lateral, 10-14 dentes pré-maxilares, 15-21 dentes no dentário, 8-10 dentes no endopterigóide, e 14 vértebras pré-caudais. A terceira espécie está amplamente distribuída na bacia do rio Parnaíba, e pode ser diagnosticada pela ausência de faixa na linha lateral, ausência da faixa médio lateral superior, 182-228 raios na nadadeira anal, 12-15 fileiras de escamas acima da linha lateral, 107-131 escamas na linha lateral, 32-34 dentes pré-maxilares, 35-44 dentes no dentário, 9-12 dentes no endopterigóides, e 13 vértebras pré-caudais. Uma chave dicotômica e o status de conservação para as três espécies são fornecidas.(AU)

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ABSTRACT Calythea Schnabl & Dziedzicki has 15 known species distributed worldwide, including three species in the neotropics. The species of Calythea can be easily identified by having bright silvery grey-dusting on the thorax and abdomen, forming a contrasting pattern with the dark body. Herein, we describe two new species from the Neotropical region and present new records of the genus for Argentina, Brazil, Chile, Colombia, Ecuador and Peru. We also redescribe Calythea comis (Stein). In addition, we present an identification key for the Neotropical species and drawings of the terminalia and habitus images of the new species, C. comis, C. crenata (Bigot) and C. micropteryx (Thomson).

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The species of Hypostomus from the Parnaíba River basin were reviewed through molecular and morphological analysis. Five species were found in the basin, including a new species herein described. The distribution of H. pusarum was expanded to this basin, and a closely related species was recorded (H. aff. pusarum), also the presence of H. johnii and H. vaillanti was confirmed. The new species is distinguished from most congeners by its large number of premaxillary and dentary teeth, a wide dental angle of 115° to 135°, presence of a rounded dark spots on a lighter background and anteromedial region of the abdomen depleted of plaques (vs. anteromedial region of the abdomen covered by platelets and odontodes in H. johnii, H. pusarum, H. aff. pusarum and H. vaillanti). Furthermore, an identification key of the species from the Maranhão-Piauí ecoregion and maps with the geographic distribution of these species are presented. The species of Hypostomus in the Parnaíba River basin have different geographic distributions, suggesting different niches or geographical barriers, providing an opportunity for ecological and evolutionary studies.(AU)

As espécies de Hypostomus da bacia do rio Parnaíba foram revisadas por meio de análises moleculares e morfológicas. Cinco espécies foram encontradas na bacia, incluindo uma nova espécie aqui descrita. A distribuição de H. pusarum foi expandida para esta bacia, uma espécie intimamente relacionada foi registrada (H. aff. pusarum), e a presença de H. johnii e H. vaillanti foi confirmada. A nova espécie se distingue da maioria das congêneres por seu grande número de dentes nos pré-maxilares e dentários, um amplo ângulo do dentário de 115° a 135°, presença de manchas escuras arredondadas em um fundo mais claro e região anteromedial do abdômen sem placas (vs. região anteromedial do abdômen coberta por placas e odontódios em H. johnii, H. pusarum, H. aff. pusarum e H. vaillanti). Além disso, é apresentada uma chave de identificação das espécies da ecorregião Maranhão-Piauí e mapas com a distribuição geográfica dessas espécies. As espécies de Hypostomus na bacia do rio Parnaíba apresentam diferentes distribuições geográficas, sugerindo diferentes nichos ou barreiras geográficas, proporcionando oportunidade para estudos ecológicos e evolutivos.(AU)

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