Taxonomic revision of the genus Anostomoides (Characiformes: Anostomidae)

Abstract

A taxonomic revision of Anostomoides is herein presented based on a comprehensive revision of specimens deposited in fish collections and the literature. The present revision proposes that A. laticeps is a junior synonym of A. atrianalis, while A. passionis is a junior synonym of Leporinus nattereri, and the latter is thus transferred to Anostomoides, forming the new combination Anostomoides nattereri. Principal Components Analysis (PCA) showed that examined specimens form two distinct morphotypes, corroborating the validity of both A. atrianalis and A. nattereri. Anostomoides nattereri is distinguished from A. atrianalis by having four branchiostegal rays (vs. three), three pores in infraorbital one (vs. four), 37–39 pored lateral-line scales (vs. 41–44), lower lip with rounded dermal papillae (vs. forming ridges), three dark rounded midlateral blotches (vs. three or four vertically elongated blotches and/or a faded dark longitudinal stripe), dark lines between scale series on posterior half of body on specimens smaller than 150 mm SL (vs. dark lines absent), a greater body depth (27.6–36.2 % vs. 24.5–38.7% of SL) and smaller interorbital distance (34.4–53.8 % vs. 42.6–67.3 % of HL). Anostomoides nattereri is distributed across several tributaries of the Amazon and Orinoco rivers, whereas A. atrianalis is widespread throughout the Amazon, Orinoco, and Essequibo basins. The genus Anostomoides is currently diagnosed based on a combination of non-exclusive characters: upturned or slightly upturned mouth with four premaxillary teeth including symphyseal tooth bicuspid or with blunt cutting edge, remaining teeth slightly tricuspid (with medial cuspid distinctly larger); four dentary teeth, symphyseal tooth with truncate cutting edge (without cusps); second tooth with a single large cusp, and two lateral teeth with three or slightly more small cusps.

A Pliocene–Pleistocene continental biota from Venezuela

“…Among the Anostomidae, premaxillary symphyseal teeth with a massive unicuspid incisiform shape are characteristics of Megaleporinus, of which eleven species are recognized (Ramirez et al 2017;Birindelli et al 2020). In contrast, Abramites, Anostomoides, and Leporinus have compressed teeth with a mesial ridge and usually a single outstanding cusp, often accompanied by smaller lateral cusps in juveniles (see Birindelli et al 2013;Assega and Birindelli 2019). Our comparisons suggest also that the specimens AMU-CURS-851 resemble the premaxillary symphyseal teeth of Megaleporinus muyscorum in size and morphology (Fig.…”

The DNA barcode reveals cryptic diversity and a new record for the genusLeporinus(Characiformes, Anostomidae) in the hydrographic basins of central northern Brazil

“…Prior to the present study, three Leporinus species were considered to be present in the hydrographic basins of the Brazilian state of Maranhão— L. affinis , in the Itapecuru basin( Abreu et al, 2019 ), L. friderici in the Itapecuru, Mearim, Maracaçumé, Munim, Periá, and Parnaíba basins ( Piorski et al, 1998 ; Soares, 2005 ; Ramos, Ramos & Ramos, 2014 ; Melo et al, 2016 ; Abreu et al, 2019 ; Brito et al, 2019 ; Brito et al, 2020 ; Guimarães et al, 2021a ; Guimarães et al, 2021b ; Guimarães et al, 2021c ), and L. piau in the basins of the Itapecuru, Mearim, Turiaçu, and Parnaíba rivers ( Barros, Fraga & Birindelli, 2011 ; Ramos, Ramos & Ramos, 2014 ; Ribeiro et al, 2014 ; Assega & Birindelli, 2019 ; Abreu et al, 2019 ). Based on analyses of molecular data, however, Fraga et al (2014) and Nascimento et al (2016) found evidence of two distinct lineages in the L. piau group from the Itapecuru basin, while in the present study, L. piau was assigned to three different clades, being associated strongly with L. cf.…”