Fraxinus L. (Oleaceae) fruits from the early Oligocene of Southwest China and their biogeographic implications

Two new fossil taxa of the ash tree, namely F. zlatkoi Meng-Xiao Wu et J.Huang sp. nov. and Fraxinus cf. honshuensis Tanai et Onoe were reported from the early Oligocene of the Lühe flora, Yunnan Province, Southwest China. The fruit traits were used to assign the proposed species to the genus Fraxinus. These traits were a flattened and symmetrical shape, a single seed located in the base of the fruit and veins parallel to the long axis of each fruit. The new species have low length to width ratio and an obovate seed. Our fossils represent the oldest records of Fraxinus in the low latitude region of the Northern Hemisphere. These fossils provide evidence that Section Dipetalae and Section Ornus had appeared in Southwest China by the early Oligocene.