19-Million-Year-Old Spondioid Fruits from Panama Reveal a Dynamic Dispersal History for Anacardiaceae

Premise of research. Recent classifications of Anacardiaceae recognize two subfamilies, Anacardioideae and Spondioideae. Most genera within Spondioideae are still recognized for having drupes with sclerified stones that vary in locule number and germination mechanisms. Spondioid fruits have been recognized in the Cenozoic fossil record of Europe, Asia, and North America. However, they have remained elusive in the Neotropics, where today they are an important component of tropical rain forests and seasonally dry tropical forests. Here, we describe three new species of fossil endocarps related to Spondias, Dracontomelon, and Antrocaryon.Methodology. Fossil endocarps were collected from the 19–18.5 Ma (early Miocene) Cucaracha Formation, Panama Canal. The fossils were studied by physical sections, acetate peels, and X-ray microtomography. The fossil endocarps were exhaustively compared with all extant genera of Spondioideae.Pivotal results. Spondias rothwellii sp. nov. and Antrocaryon panamaensis sp. nov. ar...