THE OLDEST KNOWN MENISPERMACEAE ARE FROM PATAGONIA, SOUTH AMERICA

Menispermaceae are climbing plants distributed throughout the tropics and subtropics, with a few species extending into temperate North America, Asia, and southeast Australia. Traditionally, the family was thought to have a Laurasian origin because fossil endocarps are abundant in Northern Hemisphere Cenozoic deposits; however, more recent studies using molecular phylogenetic techniques have suggested that Menispermaceae likely originated in the tropics, perhaps in Indomalasia during the Late Cretaceous-early Paleogene. Here we report the discovery of fossil Menispermaceae endocarps that challenge both hypotheses. The fossils were collected from the earliest Paleocene (65.58–64.86 Ma) deposits of the Salamanca Formation and the early Eocene (~52 Ma) deposits at Laguna del Hunco in Patagonia, Argentina. The Salamanca endocarp is the oldest unequivocal occurrence of the family in the world. Together, these fossils demonstrate that Menispermaceae were extra-tropical by the earliest Paleocene and they contribute to our understanding of the flora and environment of Patagonia following the end-Cretaceous mass extinction event. Additionally, we will present a review the fossil record of Menispermaceae in the Southern Hemisphere considering the recently revised classification of the family and will discuss the evolution and biogeographic history of the family given these new discoveries.