Studies on the presence of social boundaries or of different societies and populations in lower Parana wetlands (Argentina) have always been inferred from the material basis of the archaeological record, either from stylistic differences or by the presence / absence of certain archaeological features. This paper aims to complement these studies through the analysis of epigenetic craniofacial traits. Thirty nine individuals, from the north and south of the Parana Guazu River and, from the Flood plains and lower Delta environmental subsectors, were analyzed. The results show statistically significant differences between the latter two environmental units, given by the presence of multiple infraorbital foramina and epipteric bone among individuals from the Flood plains, and their complete absence among those from the lower Delta. These results, although preliminary, are a breakthrough for the regional archaeology, as it is the first time the existence of biological differences can be interpreted as the coexistence of different societies through analyses that exceed the intraregional comparison of artifactual variability.