Mummified Oligocene fruits of Schima (Theaceae) and their systematic and biogeographic implications

AbstractThe genus Schima includes about 20 species and is distributed only in southern China and adjacent areas of Asia. The previous molecular phylogenetic analysis suggested Schima is in the tribe Gordoniae, along with Gordonia and Franklinia. However, because few fossils have been reported, the biogeographic origin of Schima is still poorly known. In this paper mummified fossil fruits of Schima are described from the upper Oligocene Yongning Formation of the Nanning Basin, Guangxi, South China. In gross morphology, the new fossil species, Schima kwangsiensis, is similar to the extant S. superba by its pentacarpellate, loculicidally dehiscent capsules, 5 imbricate sepals, pedicels with bracteoles and marginally winged seeds. Due to its excellent preservation, the new species may provide sufficient details for understanding the early evolutionary and phytogeographic history of the genus. Morphological clustering analysis shows that the new fossil species is closely related to two extant species (S. wallichii and S. superba) in the genus, implying that they may belong to an ancient taxon that occurs earlier than the others. More importantly, this discovery represents the earliest record of this genus in Asia and it explicitly moves the fossil record back to the late Oligocene in this region.