Abstract
Abstract A new species of Corumbataia is described from Rio Maranhão, Rio Tocantins basin, central Brazil. The new species is distinguished from all congeners by the presence of a small, naked area on snout tip; by having the abdomen covered with small platelets forming a shield which reaches the lateral mid-ventral plates; by the anterior profile of the head rounded in dorsal view; by the lower lip not reaching the transversal line of the pectoral girdle; and by the presence of 28 or 29 vertebrae. High genetic divergence in mitochondrial cytochrome c oxidase subunit I (COI) further supports the validity of this new species. Our phylogenetic analysis shows a derived subclade in Corumbataia, herein named as the Corumbataia cuestae group, composed of the new species plus C. cuestae, C. tocantinensis, C. britskii, C. liliai, and C. lucianoi. This group is defined by having a conspicuous crest of hypertrophied odontodes on head; absence of the adipose fin or a single series of platelets at adipose-fin position; and anastomosis of the infraorbital and otic sensory canals over the pterotic-supracleithrum. Here we also restrict the distribution of C. tocantinensis to the Rio Araguaia basin.
Highlights
Loricariidae is the most diverse family of Siluriformes with almost 1000 valid species (Fricke et al, 2020) recognized mainly by having the body covered by bony plates, external tooth-like structures, and a ventral mouth with lips forming an oral disk used to adhere to surfaces and to soft substrate for foraging (Greerinckx et al, 2007; Garg et al, 2010)
Corumbataia was proposed by Britski (1997) when describing Corumbataia cuestae from the Upper Paraná basin in the Rio Tietê and Corumbataia tocantinensis, from the Rio Araguaia and Rio Tocantins basins
Morphometrics are given as percentages of standard length (SL), except for subunits of head expressed as percentages of head length (HL)
Summary
Loricariidae is the most diverse family of Siluriformes with almost 1000 valid species (Fricke et al, 2020) recognized mainly by having the body covered by bony plates, external tooth-like structures (odontodes), and a ventral mouth with lips forming an oral disk used to adhere to surfaces and to soft substrate for foraging (Greerinckx et al, 2007; Garg et al, 2010). Corumbataia was proposed by Britski (1997) when describing Corumbataia cuestae from the Upper Paraná basin in the Rio Tietê and Corumbataia tocantinensis, from the Rio Araguaia and Rio Tocantins basins. This genus was delimited by an exposed portion in the middle of the scapular bridge formed only by the coracoid; compound hypurals 1 and 2 completely fused to the compound hypurals 3−5; atrophic maxillary barbel, and anastomosis of the infraorbital and otic sensory canals over the pterotic-supracleitrum (Britski, 1997). Two species formerly described in Gymnotocinclus were transferred to Corumbataia by Roxo et al (2019): C. anosteos (Carvalho, Lehmann & Reis, 2008) and C. canoeiro (Roxo, Silva, Ochoa & Zawadzki, 2017)
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