not a species from Argentina:
Silurus coecutiens Lichtenstein, 1819

published in:
Vari, Richard P., Carl J. Ferraris Jr. & Mário C. C. de Pinna (2005):
The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study.
Neotropical Ichthyology 3 (2):127-238

remarks (from publication, p. 164):
…Pozzi (1945: 262) followed by Ringuelet & Arámburu (1961: 46), Ringuelet et al. (1967: 348) and López et al. (2003: 37) cited Cetopsis coecutiens from northwestern Argentina. The original Pozzi report (1945, map on page 251) indicated two localities in the Provinces of Salta and Jujuy from which species of the Cetopsinae originated, with both of those sites within the río Bermejo basin in the northwestern portion of the río de La Plata drainage system. None of the specimens of Cetopsis coecutiens examined in this study originated in the río de La Plata basin and the only species of the Cetopsinae that we examined that originated in the río Bermejo system was C. starnesi. Because of this evidence, we consider the citations of Cetopsis coecutiens from Argentina to be based on misidentifications of another species, most likely C. starnesi.