considered a species from Argentina:
Astronotus crassipinnis (Heckel, 1840)

distribution in Argentina:
floodplains and lagunas close to rios Paraguay, Paraná and Pilcomayo in Formosa and Chaco provinces

After Pozzi (1945) reported Astronotus ocellatus from ‘Río Paraná’, subsequent authors (e.g. Ringuelet et al., 1967; López et al. 1987; Liotta, 2006) considered A. ocellatus as an ‘especie limítrofe’, meaning ‘species from neighbouring countries’. López et al. (2003) included A. ocellatus for the province of Chaco, based on an illustration of Martinez (1983).
Fernandez Santos (pers. comm.) at the beginning of the 1990ies could repeatedly catch Astronotus in the Laguna de Oca, rio Paraguay basin, and small lagunas close to the town of Clorinda, rio Pilcomayo basin, both in province of Formosa. He has trustworthy information about animals that were obtained from the río Paraná close to Resistencia, province of Chaco, matching the localities of both, Pozzi and Martinez.
Kullander (1981) reported Astronotus ocellatus from Paraguay, considering Astronotus crassipinnis a synonym. Then Kullander (1986) revalidated Astronotus crassipinnis from synonymy with A. ocellatus and assigned records from the Paraguay and Paraná basin to Astronotus crassipinnis while restricting A. ocellatus to the Amazon drainage (1986, 2003).
Therefore records from localities in Argentina should be referred to as Astronotus crassipinnis.
It is striking that despite the collections efforts made in the eastern parts of Formosa and Chaco provinces apparently no collection specimen of Astronotus sp. from a locality in Argentina seems to be available yet.

published in:
Kullander, S.O. (1981):
Cichlid fishes from the La Plata basin. Part 1. Collections from Paraguay in the Museum d`Histoire naturelle de Genéve.
Revue Suisse de Zoologie 88 : 675-692

Kullander, S.O. (1986):
Cichlid fishes of the Amazon River drainage of Peru.
Swedish Museum of Natural History, Stockholm, 431 pp.

Kullander, S.O. (2003):
Family Cichlidae (Cichlids). p. 605-654
in: Reis, R. E., S. O. Kullander and C. J. Ferraris (eds.)
Check list of the freshwater fishes of South and Central America.
Edipucrs, Porto Alegre, 729 pp.