Late Oligocene fossil acorns and nuts of Quercus section Cyclobalanopsis from the Nanning Basin, Guangxi, South China.

Quercus is the largest genus within the Fagaceae and has a rich fossil record. Most of the fossil material is attributed to the subgenus Quercus based on leaves, pollen or rarely acorns and nuts. Fossil records of Q. section Cyclobalanopsis characterized by ring-cupped acorns are relatively few and especially those described based on nuts are scant. In this study, we described four new species of Quercus section Cyclobalanopsis based on mummified acorns and nuts: Q. paleodisciformis X.Y. Liu et J.H. Jin sp. nov., Q. paleohui X.Y. Liu et J.H. Jin sp. nov., Q. nanningensis X.Y. Liu et J.H. Jin sp. nov. and Q. yongningensis X.Y. Liu et J.H. Jin sp. nov. These species closely resemble the extant species Q. disciformis, Q. hui, Q. kerrii, and Q. dinghuensis. The occurrence of Q. section Cyclobalanopsis in the Oligocene stratum of Guangxi, South China, suggests that the section has diversified within its extant distribution center since the Oligocene. By combining records from other areas, we propose that the section first appeared in the middle Eocene of East Asia (Sino-Japan), has diversified in situ with a few elements scattering into West Asia and southern Europe since the Oligocene and Pliocene, respectively, and finally became restricted in East Asia since the Pleistocene. This indicates that the section originated and diversified in East Asia, before spreading into West Asia no later than the Oligocene and into southern Europe by the Pliocene. Subsequently it disappeared from South Europe and West Asia due to the appearance of the (summer dry) Mediterranean climate and widespread cooling during the Pleistocene.

First reliable Miocene fossil winged fruits record of Engelhardia in Asia through anatomical investigation.

Fossil genera with similar features to the winged fruits of the living Engelhardia Lesch. ex Blume (e.g., Palaeocarya G. Saporta) have been widely reported in Cenozoic fossil floras of the Northern Hemisphere. However, fossil winged fruits of Engelhardia with detailed anatomical structures have only been found in the upper Eocene of North America. This study reports the first Engelhardia fossil winged fruits with detailed anatomical structures in East Asia from the Miocene Erzitang Formation of Guangxi, South China. The anatomical and morphological features of the new fossils, including the unique structure of secondary septa, clearly distinguish them from other fossil genera and show unambiguously their attribution to the genus Engelhardia. This discovery suggests that Engelhardia had reached its modern distribution during the Miocene and the climate of the Guiping Basin in Guangxi during the Miocene was similar to that of present-day tropical and subtropical regions in Asia.

Fertile Woodwardia from the middle Eocene of South China and its implications for palaeogeography and palaeoclimate.

The genus Woodwardia, which together with the genera Anchistea and Lorinseria comprise the subfamily Woodwardioideae of Blechnaceae, has a disjunct distribution across Central and North America, Europe and the temperate to tropical areas of Asia. Fossil records of Woodwardia occur throughout the Paleogene and Neogene of North America, Europe and Asia. However, well-preserved fertile pinna fossils of this genus have not yet been reported in South China. In this paper, a new species, W. changchangensis Naugolnykh et Song, sp. nov. is described from the middle Eocene of the Changchang Basin, Hainan Island, South China. Macromorphological and micromorphological features of the fertile pinna show a straight pinna rachis, alternate, subtriangular pinnules, acute pinnule apices, almost entire or slightly undulate pinnule margins, long-ovoid sori, stalked sporangia and spores with wing-like folds on the surface, which are characterised in detail. Overall, the present fossil is most similar to the extant species Woodwardia japonica, which mostly grows in warm and moist environments. The discovery of this new species from the Changchang Basin of Hainan Island indicates that this genus has been distributed in the low-latitude tropical regions of South China from as early as the middle Eocene. Based on this find, and previous studies of other ferns from the same site, we infer that the climate of the Palaeo-Hainan landscape during deposition of the Changchang Formation was warm and humid, similar to conditions prevailing today across this region.

Fossil Fruits of Ceratophyllum from the Upper Eocene and Miocene of South China.

Ceratophyllum L. is a cosmopolitan genus of perennial aquatic herbs that occur in quiet freshwaters. Fossils of this genus have been widely reported from the Northern Hemisphere, most of them occurring in the temperate zone. Here, we describe two species of fossil fruits discovered from subtropical areas of China. The fossil fruit discovered from the upper Eocene Huangniuling Formation of the Maoming Basin is designated as C. cf. muricatum Chamisso, and fruits discovered from the Miocene Erzitang Formation of the Guiping Basin are assigned to the extant species C. demersum L. The discovery of these two fossil species indicates that Ceratophyllum had spread to South China by the late Eocene and their distribution expanded in subtropical China during the Miocene.