J Syst Evol

• Research Articles •    

Fossil pinnae, sporangia, and spores of Osmunda from the Eocene of South China and their implications for biogeography and paleoecology

Xiao-Yan Liu1,2,3, Yong-Dong Wang3,4, Li Wang1, Ning Zhou3,5, Li-Qin Li3,4, and Jian-Hua Jin1*   

  1. 1 State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China

    2 School of Geography Sciences, South China Normal University, Guangzhou, 510631, China

    3 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China

    4 Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China

    5 Department of Geology, Northwest University, Xi’an 710069, China

  • Received:2019-01-29 Accepted:2020-06-18 Online:2020-06-24

Abstract:

The genus Osmunda L. contains approximately 10 extant species widely distributed in tropical and temperate regions, with the greatest concentration of species in East and Southeast Asia. Osmunda is characterized by dimorphic or commonly hemidimorphic fronds with dimorphic pinnae. Its geological history has been traced back to the Triassic. Most records of the genus are based on rhizomes and rarely on pinnae bearing sporangia and spores. Here, we describe fossil pinnae, sporangia, and spores of Osmunda lignitum (Giebel) Stur recovered from the middle Eocene of the Changchang Formation in the Changchang Basin, Hainan Island and the Youganwo Formation in the Maoming Basin, Guangdong, South China. The fossils closely resemble the extant Osmunda banksiifolia (C. Presl) Kuhn of the subgenus Plenasium on the basis of their morphological and anatomical structures. The present occurrence of O. lignitum indicates subg. Plenasium flourished and extended from the high latitude regions such as Northeast China to the low latitude areas of South China during the middle Eocene. Large numbers of specimens described here also indicate that Osmunda was the dominant understory fern element beneath mixed evergreen broad‐leaf angiosperm and gymnosperm forests living in a warm and humid environment.

Key words: biogeography, Eocene, Osmunda, paleoecology, South China, sporangia