not a species from Argentina or Uruguay:
Oligosarcus hepsetus (Cuvier, 1829)
Koerber, S. & W.S. Serra (2020):
On the erroneous records of Oligosarcus hepsetus (Cuvier, 1829) from Argentina and Uruguay.
Ichthyological Contributions of PecesCriollos 67: 1-7
abstract (from publication):
For more than 150 years Oligosarcus hepsetus (Cuvier, 1829) has been considered to be distributed in the freshwaters of Argentina and Uruguay. An analysis of literature accounts revealed that the records of this species from these countries were erroneous due to misidentifications with either Oligosarcus oligolepis (Steindachner, 1867) or O. jenynsii (Guenther, 1864).