Among materials extracted from early Miocene strata of the Chenque Formation (Patagonia, Argentina), polyads of Acacia-pollenites myriosporites (Cookson) Mildenhall and Polyadopollenites sp. (= Anadenanthera aff. macrocarpa) were discovered. Recent affinities with polyads of Acacia (subg. Phyllodinae) and Anadenanthera respectively, exist. The presence of the Mimosoideae corroborates, for the early Miocene of Patagonia, the convergence of two types of floras which today inhabit two different warm-temperate regions, namely neotropical America and Australia. This discovery also enlarges the known paleogeographic distribution ranges of both taxa.