Estudio morfo-anatómico de frutos de palmeras de la formación Chichinales (mioceno inferior) procedentes de paso córdoba, Provincia de Río Negro, Argentina.

Abstract

The Area Natural Protegida Paso Córdoba (ANPPC) in the Río Negro province (Argentina) has Lower Miocene outcrops that belong to the Chichinales Formation. The fossil record of this unit is restricted to its lower section and includes a diverse fauna. Regarding the fossil flora, only permineralized woods assigned to Nothofagoxylon menendezii Ragonese and other plant remains still not studied have been recorded. Based on the review of materials from collections and new samplings from fieldwork, abundant fruits, and stems of palm trees (Arecaceae) have been identified. The fruits (drupes) are preserved in large concentrations in sandstone banks with a cross-shaped structure. They consist of pyrenes preserved as permineralizations and molds which constitute the subject of study of the present work. All the specimens studied were included in the fossil genus Palmocarpon Lesq. The morphological and anatomical characteristics of the fossil fruits were compared with those of several groups of fossil and extant palms, allowing their assignment to the subtribe Attaleinae (Cocoseae, Arecoideae) with a high degree of confidence. These fruits constitute the first fossil record of Attaleinae for southern South America, being one of the most reliable fossil records of this subtribe for the continent. Anatomically preserved palm stipes and other coniferous logs have been found associated with the fruits. The abundance and wide spatial distribution of the palm record in the lower section of Chichinales Formation suggests that during the Lower Miocene a plant community developed in the area in which palms constituted one of the dominant elements of the tree stratum and most likely as open communities.