Casuarinaceae from the Eocene of Patagonia, Argentina

Casuarinaceae, today restricted to the Australasian region, has an extensive fossil record. In this article, we evaluate previous records and recent findings from Patagonia, where Casuarinaceae are known from the Tufolitas Laguna del Hunco (early Eocene) in northwestern Chubut, Argentina. Based on characters found in numerous branchlets, infructescences, and male inflorescences with pollen of the Haloragacidites harrisii type, the presence of three fossil species within the genus Gymnostoma is confirmed: G. patagonicum comb. nov., G. archangelskyi sp. nov., and G. argentinum sp. nov. This is the oldest worldwide report of male inflorescences and the first record of vegetative branchlets and male inflorescences for South America. These fossils are of particular interest because Casuarinaceae is now extinct in South America, and they support the view that the family was diverse and had widespread distribution during the early Eocene climatic optimum. The diverse Gymnostoma described here further strengthens biogeographic links between Paleogene floras of Patagonia and Australasia.