not species from Argentina:
Pyrrhulina brevis Steindachner, 1876
Pyrrhulina melanostoma (Cope, 1870)

In López et al. 2003 both species are listed as valid and from Argentina.

published in:
Zarske, A. & J. Gery (2004):
Zur Variabilitaet von Pyrrhulina australis Eigenmann & Kennedy, 1903 (Teleostei: Characiformes: Lebiasinidae).
Zoologische Abhandlungen des Staatlichen Museums für Tierkunde, Dresden 54: 39-54

exstract from publication (translated from German by Stefan Koerber):
Besides the species discussed in this work, Ringuelet et al. (1967) and Lopez et al. (2003) list two or three further species for Argentina: (1) Pyrrhulina brevis Steindachner, 1876…(2) P. laeta (Cope, 1872)…and (3) P. melanostoma (Cope, 1870). Distribution of these species, which originate from upper and central Amazonia, in southern South America is highly unprobable…
(1) Pyrrhulina brevis Steindachner, 1876. This record is based on a work of Perugia (1891), published prior to the description of P. australis Eigenmann & Kennedy, 1903. Hereby a wrong determination is more than probable. The type material of P. brevis in MNW consists of two species, both distributed far more north. …
(3) P. melanostoma (Cope, 1870). Lopez et al. (2003) quote Meinken (1937) as source for the record of P. melanostoma from Argentina. In that work P. melanostoma is not mentioned. Meinken (1937) refers to the two fishes…he worked on as “Pyrrhulina semifasciata Steindachner”. These two fishes are still deposited at ZMB 23833 and without doubt are specimens of P. australis