Mummified fruits of Choerospondias nanningensis sp. nov. (Anacardiaceae) from the upper Oligocene of a low latitude site in East Asia

Extant species of Choerospondias (Anacardiaceae) are mainly distributed in the tropical and subtropical areas of East Asia. However, the fossil record indicates that the genus was more widespread in the past, with Cenozoic occurrences in both Europe and Asia. We investigated the pericarp anatomy of well-preserved mummified fossil fruits of Choerospondias from the upper part of Yongning Formation (late Oligocene) of the Nanning Basin, South China. These fruits are recognized as a new species Choerospondias nanningensis sp. nov. This is the lowest latitude fossil occurrence for the genus, and the first fossil record of this genus from its modern area of distribution (South China), indicating that Choerospondias had spread into its modern area of distribution by the Oligocene. In this study, we also investigated the pericarp anatomical structure of the one extant species of Choerospondias. We found that this genus has an endocarp morphology and anatomy typical of the Spondioideae. This is the first study focusing on the pericarp anatomy of fossil and extant species of Choerospondias simultaneously. This study provides new fossil evidence for further understanding the phylogeny of this genus, and contributes significantly to the knowledge of fruit morphology of the family Anacardiaceae.