Late Miocene Leaves and Endocarps of Choerospondias (Anacardiaceae) from Zhejiang, Eastern China: Implications for Paleogeography and Paleoclimate.

Abstract

Simple SummaryChoerospondias endocarp and leaf fossils were found in the Shengxian Formation of Zhejiang, eastern China. We performed cuticle analysis on leaves and micro-CT on endocarps to reconstruct three-dimensional morphological characteristics. Fossil records suggest that Choerospondias spread from low to middle latitudes throughout geological time, and migrated to the northern boundary of the distribution range in China during the late Miocene. Based on the climatic parameters under which extant Choerospondias live, the paleoclimatic values of eastern Zhejiang in the late Miocene were obtained and compared with previously published paleoclimatic data. The results suggest that the climate of the late Miocene in the Tiantai region of Zhejiang was warm and humid, similar overall to the modern climate of this region.Choerospondias (Anacardiaceae), characterized by radially arranged germination pores near the top, is a monotypic genus mainly distributed in subtropical and tropical eastern Asia, while fossil records indicate a wide distribution throughout Eurasia during the Cenozoic. In this study, we reported three-dimensionally preserved Choerospondias endocarps, and the associated compressed leaves from the late Miocene Shengxian Formation in Tiantai, Zhejiang, eastern China. The plant remains were assigned to two new fossil species. The endocarps were identified as Choerospondias tiantaiensis sp. nov., and the leaves were identified as Choerospondias mioaxillaris sp. nov. Based on fossil records and climate fluctuation during the Cenozoic, we conclude that Choerospondias may have originated from Europe in the early Eocene and then spread to Asia along the coast and island chains of the Tethys and Paratethys oceans. The distribution position of the current fossils was adjacent to the northern boundary of the modern distribution of Choerospondias in East Asia, indicating that the distribution pattern of Choerospondias in East Asia likely formed no later than the late Miocene. We reconstructed the late Miocene paleoclimate of eastern Zhejiang by using the method of climate analysis of endemic species (CAES), and then compared it to the data reconstructed in previous studies. The results indicate that the late Miocene climate in eastern Zhejiang was similar to or warmer and more humid than the modern climate in this region.