not from Argentina:
Hypostomus alatus Castelnau, 1855
Hypostomus hermanni (Ihering, 1905)
Hypostomus itacua Valenciennes, 1836
Hypostomus paulinus (Ihering, 1905)

published in:
Bogan, S., V.E. Méttola, G.E. Terán & Y.P. Cardoso (2024):
The ’cascudo amarello’ Hypostomus luteus (Godoy, 1980) in Argentina.
Historia Natural 13 (3): 5-15

abstract (from publication):
A batch of Hypostomus luteus collected in the Uruguay River basin in the province of Misiones is described. The specimens analyzed here allow this species to be safely incorporated into the lists of fish present in the Argentine Republic. In addition, descriptions are provided that we consider useful for the recognition of this species. After reviewing the lists containing Hypostomus for Argentina, we propose to eliminate four species that are actually not present in our waters or whose description makes their reliable geographic or taxonomic location impossible. By this we limit the list of Hypostomus species with a confirmed Argentinean distribution to 22 species.

remark (from publication):
Koerber and Weber (2014) stated that H. alatus, H. itacua, H. hermanni and H. paulinus have dubious or uncertain presence. We agree with this latter proposal and consider that these species should be eliminated from the species list confirmed for Argentina.