Two new, remarkably colored species of the Neotropical catfish genus Cetopsorhamdia Eigenmann & Fisher, 1916 (Siluriformes, Heptapteridae) from Chapada dos Parecis, western Brazil, with an assessment of the morphological characters bearing on their phylogenetic relationships

Abstract

Two new species of heptapterid catfish genus Cetopsorhamdia are described from close localities in western Brazil, at Chapada dos Parecis, an area with extremely high level of endemism. One species is from the upper Rio Madeira system, Rondônia State, and the other from the upper Rio Tapajós system, Mato Grosso State. The two species are diagnosed, among several other features, by their markedly distinctive color patterns, with the former having well-defined quadrangular marks in trunk flanks while the latter bearing irregular, vertical bars along the trunk. The monophyly of Cetopsorhamdia is discussed, with two putative synapomorphies being proposed to support the genus. Potentially informative morphological characters to resolve the internal relationships of the genus are presented and discussed. Despite the striking external differences between the two species herein described, they are found to likely form a clade.

A new cryptic species of Imparfinis (Siluriformes: Heptapteridae) from the Orinoco River basin, revealed by an iterative approach

“…picklei , whose morphological similarity in size, body shape and pigmentation pattern is remarkable (Figure 4f), suggesting a similar occupancy of the habitat by both species. Nonetheless, these two species are easily differentiated by conspicuous external features, such as the relative length of the maxillary barbel, adipose‐fin base and lower lobe of caudal fin, as well as diagnostic characters defining both genera (Bockmann, 1998; Bockmann & Reis, 2021; Bockmann & Slobodian, 2018).…”

Fish fauna of moderate altitude from first order stream in upper Rio Machado, Rondônia, Brazil

“…Its headwaters are located at the southeastern border of Rondônia at Chapada dos Parecis, a watershed between three river basins (Madeira, Paraguay and Tapajós). This region is also the type locality of many recently described fish species (Fisch-Müller et al, 2005;Wingert & Malabarba, 2011;Ohara & Lima, 2015;Ohara & Marinho, 2016;Bockmann & Reis, 2021;Marinho et al, 2021). The majority of these species seem to have very restricted distribution, since they were not recorded during previous surveys in the Rio Machado basin (e.g., Perin et al, 2007;Casatti et al, 2013;Costa et al, 2017), in other rivers of the Rio Madeira basin (e.g., Rapp Py-Daniel et al, 2007;Araújo et al, 2009;Pedroza et al, 2012;Queiroz et al, 2013a, b;Vieira et al, 2016;Anjos et al, 2019;Oliveira et al, 2020), or in neighboring drainages (Ohara & Loeb, 2016;Ohara et al, 2017).…”