A tropical forest of the middle Miocene of Fujian (SE China) reveals Sino-Indian biogeographic affinities

Abstract

The middle Miocene Fotan flora of Zhangpu County, South Fujian, China has been considered to represent tropical rainforest based on the occurrence of distinctive winged fruit fossils of the Dipterocarpaceae. However, this paleoclimatic interpretation has been challenged. In this study, we describe new tropical and subtropical elements of this flora that co-occurred with Dipterocarpaceae based on newly collected fossil leaves from the Fotan flora. The fossils were identified through detailed comparison with leaves of living plants. Six new species belonging to six different families are described: Artocarpus basirotundatus sp. nov. (Moraceae), Bauhinia fotana sp. nov. (Leguminosae), Boehmeria fujianensis sp. nov. (Urticaceae), Calophyllum striatum sp. nov. (Calophyllaceae), Flacourtia serrulata sp. nov. (Salicaceae), and Macaranga stellata sp. nov. (Euphorbiaceae). They represent the first fossil records of these genera in China, with the exception of Bauhinia. These elements provide further evidence for the recognition of tropical forest in South Fujian during the middle Miocene. They show more affinities with Indian Neogene floras than with other Chinese palaeofloras. It suggests that, during the Mid-Miocene Climatic Optimum, the border between the tropical and subtropical vegetation moved north to South Fujian. The Fotan palaeoflora is the first record of Miocene floristic affinities between Indian and South Chinese floras. In contrast, the southwestern Chinese Miocene palaeofloras have a different floristic composition without clear Indian affinities. We propose that the route of exchange between the Indian and South Chinese Miocene floras passed through South-East Asia.