CITRUS LINCZANGENSIS SP. N., A LEAF FOSSIL OF RUTACEAE FROM THE LATE MIOCENE OF YUNNAN, CHINA

摘要

Premise of research. The origin and phytogeographic history of Citrus (Rutaceae) is poorly known, partly because of the very limited fossil record of this genus. Our newly discovered fossil materials confirm the existence of Citrus in the late Miocene in Asia. Methodology. Fossil leaves were collected from the field, carefully exposed in the laboratory, and investigated through comparison of architectural characters with extant leaves. Pivotal results. A new species, Citrus linczangensis sp. n., from the late Miocene of Lincang, Yunnan, China, is characterized by unifoliolate compound leaf morphology, an articulated and broadly winged petiole, and an entire margined leaflet with basal intramarginal veins. Conclusions. The unique morphological characters of this fossil provide definitive evidence of Citrus in the fossil record of Asia and expand the geological history of the genus back to the late Miocene. The new fossil material gives some clues for the origin of modern Citrus species and supplements knowledge of the Lincang fossil flora.