Abstract
Abstract The typical long-snouted species of Corydoras from the río de La Plata basin were reviewed herein, and the previously proposed synonymy of Corydoras ellisae was corroborated. Corydoras areio and C. aurofrenatus are diagnosed from their congeners, excluding those in lineage 1, by the following features: temporal sensory canal in sphenotic with two pores; upper tooth plate of branchial arch with three or four series of teeth; fleshy flap at mouth corner. Corydoras areio differs from all lineage 1 congeners by having infraorbital 2 with relatively wider posterior laminar expansion; absence of large patches of black pigmentation on the body and absence of conspicuous concentration of dark brown or black chromatophores on anterior portion of the dorsal fin; and presence of blotches on flanks not aligned in longitudinal series. Corydoras aurofrenatus differs from all lineage 1 congeners by having ventral surface of head and trunk densely covered by small, not coalescent platelets; middle portion of flank with two or three dark brown or black patches (below the dorsal-fin, below the adipose-fin base, and on the caudal peduncle base, diffuse and variably present), patches decreasing in size posteriorly; poorly developed fleshy flap at the corner of mouth; anteroventral portion of cleithrum exposed.
Highlights
Callichthyidae is composed of armoured catfishes with two longitudinal series of dermal plates on flanks, currently comprising more than 200 species (Reis, 2003; Fricke et al, 2020)
Corydoras areio can be distinguished from the species belonging to the lineage 1, except for C. acutus Cope, 1872, C. cervinus Rössel, 1962, C. maculifer Nijssen, Isbrücker, 1971, C. oxyrhynchus Nijssen, Isbrücker, 1967, C. saramaccensis Nijssen, 1970, C. vittatus Nijssen, 1971 and C. zawadzkii Tencatt & Ohara, 2016, by the absence of large patches of black pigmentation on the body
Corydoras areio is diagnosed from C. acutus, C. cervinus, C. maculifer, C. vittatus and C. zawadzkii by the presence of blotches on flanks not aligned in longitudinal series
Summary
Callichthyidae is composed of armoured catfishes with two longitudinal series of dermal plates on flanks, currently comprising more than 200 species (Reis, 2003; Fricke et al, 2020). Corydoras Lacépède, 1803, its largest genus, currently contains 175 species, making it the most species-rich genus of Siluriformes (Tencatt et al, 2019; Lima, Britto, 2020). Kennedy (1903) provided a revised catalogue of a fish collection from Paraguay sent to the Indiana University by Juan Anisits. This collection comprises a total of 750 specimens from many localities of Paraguay, including material collected by Carl Ternetz at Asuncion, and from Descalvados, State of Mato Grosso, Brazil. One of them is Corydoras aurofrenatus Eigenmann & Kennedy, 1903, a typical long-snouted species from lineage 1 sensu Alexandrou et al (2011) described based on a single specimen captured in Aguada, near arroyo Trementina, río Paraguay basin, Paraguay. Kennedy (1903) mentioned that this species displays a very peculiar color pattern among Corydoras species, with “no color on sides, belly or breast” (p. 508), dorsal and caudal fins spotted and “a broad yellow band across the snout” (p. 508)
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