Two new species of Odontostilbe historically hidden under O. microcephala (Characiformes: Cheirodontinae)

Abstract

Specimens historically identified as Odontostilbe microcephala from the upper rio Paraná and Andean piedmont tributaries of the río Paraguay are reviewed and split in three species. We found that the distribution of O. microcephala is restricted to the Andean slope of the río Paraguay basin. The species is distinguished from congeners with subterminal mouth by the elongate body, usually 10-12 gill rakers on upper branch and smaller horizontal orbital diameter (24.6-32.8 % HL, mean 28.7%). Specimens from upper rio Paraná constitute two new species, diagnosed from other Cheirodontinae by the presence of mesopterygoid teeth, grouped on median portion and forming a continuous row. The new species are distinguished from each other by having premaxillary teeth with five cusps vs. nine cusps and by the number of lamellae in left and right sides of central median raphe of olfactory rosette with 20-21 vs. 11-12.Keywords: Biodiversity, Characidae, La Plata River basin, Mesopterygoid teeth, Taxonomy.Espécimes historicamente identificados com Odontostilbe microcephala do rio Paraná e tributários do río Paraguay, foram revisados e separados em três espécies. A distribuição de O. microcephala é restrita ao sopé andino da bacia do río Paraguay. A espécie é distinta das congêneres com boca subterminal pela forma alongada, geralmente 10-12 rastros branquiais no ramo superior e menor diâmetro horizontal da órbita (24,6-32,8 % CC, média 28,7%). Espécimes do alto rio Paraná constituem duas espécies novas diagnosticadas de outros Cheirodontinae pela presença de dentes no mesopterigoide, agrupados em sua porção média e formando uma fileira continua. As novas espécies distinguem-se por ter dentes premaxilares com cinco cúspides vs. nove cúspides e pelo número de lamelas nos lados esquerdo e direito da rafe central da roseta olfativa com 20-21 vs. 11-12.Palavras-chave: Bacia do rio da Prata, Biodiversidade, Characidae, Dentes do Mesopterigoide, Taxonomia.

Ichthyofauna of streams of the Rio Sapucaí basin, upper Rio Paraná system, Minas Gerais, Brazil

“…Odontostilbe weitzmani Chuctaya, Bührnheim, & Malabarba, 2018, a species recently described from the upper Paraná system (Chuctaya et al 2018), has previously been collected at R1 (DZSJRP 20445, 2014 year). However, this species was not collected during this survey.…”

Species delimitation in a range‐restricted group of cascudinhos (Loricariidae: Epactionotus) supports morphological and genetic differentiation across coastal rivers of southern Brazil

“…Before statistically analysing morphometric data, the VARSEDIG algorithm (Chuctaya et al, 2018;Faustino-Fuster et al, 2019;Guisande et al, 2016;Leigh & Bryant, 2015) (Anderson, 2001). The same data set was used in both PCA and linear discriminant analysis (LDA), also performed in Past, to, respectively, search for general patterns of variation among specimens (Leal & Sant'Anna, 2006) and assess between-group patterns of body shape variation.…”

Two new species of Heptapterus (Siluriformes: Heptapteridae) from the Uruguay River basin, Brazil

“…All morphometric variables were standardised against standard length before use in statistical analyses. The VARSEDIG algorithm was used to identify the morphometric characters that significantly discriminate between two taxa and validate the morphological distinctness between them (Chuctaya et al, 2018;Guisande et al, 2016;Leigh & Bryant, 2015).…”