Paleofloristic assemblage from the Paleogene Río Guillermo Formation, Argentina: preliminary results of phylogenetic relationships of Nothofagus in South America

Abstract

Hünicken's paleobotanical collection is one of the most important in South America because it was the first one to be related to a documented stratigraphic profile. This floristic assemblage (Oligocene) recovered from Río Guillermo Formation, at Estancia Tres Marías, Río Guillermo Valley, Santa Cruz, Argentina, is described by the first time in this paper. Five species of genus Nothofagus (N. subferruginea, N. serrulata, N. crenulata, N. elongata and N. variabilis) together with Myrcia bagualense are components of the assemblage. The presence of Acaena brandmayri is confirmed for the first time for the area. Paleoenviromental and paleoclimate implications are also discussed. Characteristic species from a temperate-cold climate such as the genus Nothofagus are present in the material studied. A phylogenetic study of the fossil species herein described and the extant South American species of Nothofagus is presented. The preliminary results support the hypothesis that fossil species of Nothogafus are closely related to the modern species.