Oldest Known Malpighiaceae Fossils: Early Eocene Patagonian Fruits Support a Wide Paleolatitudinal Distribution

Premise of research. Although the biogeographic history of the largely Neotropical family Malpighiaceae is extensively studied, fossils of the group, which are critical for constraining evolutionary scenarios, are notably limited. Here, we present our discovery of fossil fruits of Malpighiaceae from the early Eocene (52 Ma) West Gondwanan Laguna del Hunco flora (Chubut, Argentina). Methodology. We describe the new fossils, explore their taxonomic position using phylogenetic analyses of combined morphological and molecular data, and assess their biogeographic implications. Pivotal results. The fossils share several morphological features with the extant Neotropical genera Tetrapterys, Glicophyllum, and Niedenzuella, and they conform completely with the morphological features of Tetrapterys, leading to their placement within the genus. This discovery establishes the presence of Malpighiaceae in the Laguna del Hunco paleoflora, representing the first fossil record of Malpighiaceae fruits for the Southern Hemisphere and the oldest reliable Malpighiaceae fossils worldwide. Conclusions. The new fossils show Gondwanan history for the tribe Hiptageae and the Malpighiaceae as a whole. The new fossils from temperate South America, when combined with other fossil occurrences of the family, suggest a global distribution of Malpighiaceae by the Eocene that later contracted toward the equator.