Abstract
Abstract Two new species of Corydoras are described from the rio Madeira basin, Brazil. The intermediate long-snouted new species can be distinguished from its congeners by presenting the following combination of features: posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the spine; presence of two longitudinal black stripes on flanks; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; absence of a conspicuous black marbled coloration pattern on head; black spots on caudal fin, some spots arranged, forming transversal bars; and brownish dorsal-fin spine. The short-snouted new speciescan be distinguished from its congeners by the following combination of features: short mesethmoid; posterior laminar expansion of infraorbital 2 very reduced, not in contact with compound pterotic; two or three longitudinal black stripes on flanks; absence of an oblique or vertical black blotch across the eye; anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; and ventral surface of trunk naked or covered by sparse platelets.
Highlights
Corydoras Lacépède, 1803 is the most species-rich genus of Siluriformes, comprising approximately 170 valid species (Reis, 2003; Eschmeyer, 2015)
Nijssen & Isbrücker (1980) were the first to implicitly recognize a convergent color pattern by placing C. arcuatus Elwin, 1939 and C. narcissus Nijssen & Isbrücker, 1980, two species with almost equal color pattern, into two different morphological groups, and noting that C. narcissus is more similar to C. acutus Cope, 1872 than to C. arcuatus
Corydoras pavanelliae can be distinguished from C. axelrodi, C. evelynae, C. loxozonus, C. parallelus, C. schwartzi and C. surinamensis by the absence of an oblique or vertical black blotch across the eye; from C. axelrodi, C. evelynae, C. loxozonus, C. parallelus and C. surinamensis by presenting anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern; from C. evelynae and C. schwartzi by having ventral surface of trunk naked or covered by sparse platelets
Summary
Corydoras Lacépède, 1803 is the most species-rich genus of Siluriformes, comprising approximately 170 valid species (Reis, 2003; Eschmeyer, 2015). Multiple studies have noted apparent cases of convergence of color pattern in Corydoras. Britto et al (2009) later described a third species with very similar color pattern to C. arcuatus and C. narcissus and showed that all three species belong to distinct clades. The authors noted multiple cases of apparent convergence of color pattern within syntopic representatives of these clades, and provided evidence to support a hypothesis of Müllerian co-mimicry. During a recent field expedition in the rio Aripuanã and its tributaries in the rio Madeira basin, two new species with similar color pattern but showing divergent snout morphology were found. We describe these two sympatric and syntopic species and demonstrate that they have similar color pattern, they belong to clearly distinct morphological groups that correspond to different lineages sensu Alexandrou et al (2011)
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