PALYNOLOGICAL STUDY OF SPORES FROM SALTO DEL MACHO FORMATION, PALEOGENE OF THE ÑIRIHUAU BASIN, ARGENTINA. The first palynological data from the type locality of the Salto del Macho Formation, at the Río Foyel section, Ñirihuau Basin, Argentina, is here presented. Nineteen taxa of trilete and monolete spores of Bryophyta and Tracheophyta (Lycopsida and Polypodiopsida) belonging to the following genera were recorded: Anthocerisporis, Azolla, Baculatisporites, Biretisporites, Cingutriletes, Cyatheacidites, Cyathidites, Ischyosporites, Laevigatosporites, Matonisporites, Muricingulisporis, Peromonolites, Polypodiisporites, Reboulisporites, Retitriletes, Trilites and Tuberculatosporites. The palynoflora is dominated by representatives of the Class Polypodiopsida, with predominant Cyatheaceae and Dicksoniaceae, in asociation whith Osmundaceae and Blechnaceae. The comparison of the record of spores with that of other Paleogene/early Neogene basins from Argentinian Patagonia, Chile and Antartica, made through the PAST program, shows remarkable palynofloristic similarities between Salto del Macho Formation with the spore associations recorded in the Río Foyel, Chenque and San Julián formations. The accompanying palynoflora (Nothofagaceae, Podocarpaceae, Araucariaceae, Myrtaceae, Botryococcus braunii and low diversity of dinocysts) suggests a marginal-marine enviroment, in conditions of sub-normal salinity and temperate-warm water temperature.