Two new species of the genus Corydoras (Ostariophysi: Siluriformes: Callichthyidae) from northwestern Argentina, and redescription of C. micracanthus Regan, 1912

The group herein denominated as the Corydoras micracanthus species-group is supported by presenting dorsal and pectoral spines length reduced; caudal fin slightly emarginated; low body depth; parieto-supraoccipital process and nuchal plate not in contact and small eyes for the genus. It comprises Corydoras micracanthus, herein redescribed, and two new species described in the present paper, all from northwestern Argentina. Corydoras gladysae, a new species from the Calchaqui river, is distinguished from other species of the genus by the caudal-fin shape, slightly emarginated and by presenting the shortest dorsal and pectoral spines length (mean = 9.2 % and 14.8 % of SL, respectively). Corydoras petracinii, a new species from the Las Costas river, is distinguished from its congeners by the following combination of characters: dorsal spine short (mean = 16.6 % of SL), pectoral spine short (mean = 18.3 % of SL), body moderately elongate (body depth 29.5 % SL mean), caudal fin slightly forked and trunk flanks with 5–7 subsquare differenced blotches in the middle region. Corydoras micracanthus, from the Mojotoro river basin, is defined by its higher number of dorsolateral body plates (24–26) and trunk color pattern, presenting 4 to 6 subsquare blotches well differentiated in the flanks. The inclusion of these species into the genus Corydoras is discussed.