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

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 Choerospondiastiantaiensis 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.

A New Species of Comptonia (Myricaceae) from the Early Miocene of Central Inner Mongolia, China, and Phytogeographic History of Sweet-Fern.

Comptonia (Myricaceae) is well known as a monotypic genus living only in eastern North America; however, fossils show that the genus occurred extensively in the Northern Hemisphere during the Cenozoic. We observed dozens of Comptonia leaf fossils from the early Miocene in Zhuozi, China. The leaf architecture characteristics and epidermal features of the fossil specimens are described in detail here for the first time, and they were assigned to a new species: Comptonia hirsuta. The fruit fossils collected simultaneously from the same layer were assigned to Comptonia tymensis. The global fossil records indicate that the spatial distribution range of Comptonia reached its peak in both the Eocene and Miocene as two warm periods and then gradually decreased in the Oligocene, as well as after the late Miocene, because of the cooling global climate. Furthermore, the Comptonia taxon in East Asia may have migrated from North America via the Bering route in the late Paleocene or Eocene. Plant exchange between western Europe and eastern North America possibly occurred during the Eocene via the Thulean route. Phytogeographic variation in the Comptonia fossils from China also indicates that the reason for the disappearance of Comptonia from China may not only be due to the prolonged cooling and drying after the late Miocene, but also due to its progenitive pattern.