Fossil cashew nuts from the Eocene of Europe: biogeographic links between Africa and South America

Cashew nuts have been identified among compression fossils from the early Middle Eocene lake sediments of Messel, Germany. These fossil fruits confirm that the cashew genus,Anacardium, was formerly distributed in Europe, remote from the modern native distribution in Central and South America.Anacardium germanicumsp. n. shows that the characteristic inflated pedicel, or “cashew apple,” which facilitates biotic dispersal of cashew nuts, evolved at least 47 million yr ago. It was previously proposed thatAnacardiumand its African sister genus,Fegimanra, diverged from their common ancestor when the landmasses of Africa and South America separated. However, the paleobotanical data indicate a connection via the Northern Hemisphere with Europe as an important footstep in the spread of this clade between Africa and the New World. The former North Atlantic landbridge connecting North America and Europe via Greenland is implicated in the phytogeographic spread ofAnacardiumduring the Early and Middle Eocene.