A new species of Eigenmannia Jordan & Evermann (Gymnotiformes: Sternopygidae) from rio Tapajós, Brazil, with discussion on its species group and the myology within Eigenmanniinae

Abstract

A new species of Eigenmannia is described from the rio Mutum, tributary of upper rio Juruena, rio Tapajós basin, Comodoro, Mato Grosso, Brazil. The new species is distinguished from all congeners by coloration pattern, position of the mouth, number of scales rows above lateral line, number of premaxillary and dentary teeth, number of precaudal vertebrae, orbital diameter, mouth width, relative depth of posterodorsal expansion on infraorbitals 1+2 and relative size of coronomeckelian bone. Comments on potentially useful characters in phylogenetic studies derived from musculature, discussion on Eigenmannia species-group and the first dichotomous key for Eigenmannia are provided.

New species of glass knifefish genus Eigenmannia (Gymnotiformes: Sternopygidae) with comments on the morphology and function of the enlarged cephalic lateral‐line canals of Sternopygidae

“…The new species can be further distinguished from E. sirius by the morphology of the anterior displaced haemal spine, which is slightly cylindrical ( vs . blade‐shaped; Peixoto & Ohara, 2019: Figure 7). It differs from E. waiwai by the counts of precaudal vertebrae, 14–16 ( vs .…”

“…Data analysis was carried out on both morphometric and meristic data to test statistical differences between the new species and Eigenmannia sirius Peixoto & Ohara, 2019, a taxon with which the new species shows strong resemblance. Non‐parametric ANCOVA was implemented following Kloke and McKean (2014) using the package npsm (Kloke & McKean, 2019) for differences in pectoral‐fin length between both species.…”

“…These canals exhibit a mosaic of narrow and widened canals (Albert, 2001; Mago‐Leccia, 1978; Tagliacollo et al ., 2016) in a morphology so far registered to few fishes of unrelated taxa, such as Cyprinidae (Reno, 1971), Gasteropelecidae (Pastana et al ., 2020) and Pleuronectidae (Sakamoto, 1984). Among sternopygids, Eigenmannia Jordan and Evermann 1896 is currently the most species‐rich genus, comprising 26 valid species, with at least half of its diversity described in the past decade (Fricke et al ., 2020; Herrera‐Collazos et al ., 2020; Peixoto & Ohara, 2019). Species of the genus are distributed along Central and South America, ranging from the Rio Tuíra basin in Panamá to the Rio de La Plata basin in Argentina (Peixoto et al ., 2015), with its greatest species diversity found in the Amazon basin, where approximately half of the known species are found (Peixoto & Ohara, 2019).…”

“…Among sternopygids, Eigenmannia Jordan and Evermann 1896 is currently the most species‐rich genus, comprising 26 valid species, with at least half of its diversity described in the past decade (Fricke et al ., 2020; Herrera‐Collazos et al ., 2020; Peixoto & Ohara, 2019). Species of the genus are distributed along Central and South America, ranging from the Rio Tuíra basin in Panamá to the Rio de La Plata basin in Argentina (Peixoto et al ., 2015), with its greatest species diversity found in the Amazon basin, where approximately half of the known species are found (Peixoto & Ohara, 2019).…”

“…Despite several recent taxonomic contributions (Campos‐da‐Paz & Queiroz, 2017; Dutra et al ., 2017, 2018; Herrera‐Collazos et al ., 2020; Peixoto et al ., 2015; Peixoto & Ohara, 2019; Peixoto & Waltz, 2017; Peixoto & Wosiacki, 2016; Waltz & Albert, 2018), the monophyly of Eigenmannia still awaits further phylogenetic studies, and currently its infrageneric classification is based on informal groups of species (see discussion in Peixoto & Ohara, 2019: Table 2). Among these, the Eigenmannia trilineata species group allocates the highest number of species and encompasses taxa that exhibit a midlateral stripe between the LL and the proximal portion of the pterygiophores of the anal fin, named the ‘superior midlateral stripe’ (Peixoto et al ., 2015; Peixoto & Wosiacki, 2016).…”