New costapalmate palm leaves from the Oligocene Ningming Formation of Guangxi, China, and their biogeographic and palaeoclimatic implications

Abstract

New palm leaves from the Oligocene Ningming Formation are placed into the morphogenus Sabalites because of their costapalmate leaf shape. Four taxa are described on the basis of leaf compressions with cuticular structure. S. guanxiensis sp. nov. is characterised by hypostomatic leaf blades with a stout costa and a symmetrical base. Sabalites cf. asymmetricus has amphistomatic leaf blades with a long, delicate costa and an asymmetrical base. Sabalites sp. 1 has amphistomatic leaf blades with a long, massive costa and wide segments. Sabalites sp. 2 is characterized by hypostomatic leaf blades with a prominent costa and an asymmetrical base. The four new palm taxa expand our understanding of the floristic elements and features of the Oligocene Ningming flora. Together with the other three palm taxa that were previously reported from the Ningming Formation, our material indicates that the Oligocene Ningming flora had a rich diversity of costapalmate palms. The relatively high species diversity of palms and other plants corroborate that the Oligocene Ningming flora represents a warm and humid climate.

Keywords:

• Oligocene
• Arecaceae
• Ningming Formation
• China
• biogeography
• palaeoclimate

Acknowledgments

We are grateful to Dr Dian-Xiang Zhang and Dr Fei-Yan Zeng for their permission to access the extant Arecaceae specimens for comparison, to Dr John Dransfield and Dr Rashmi Srivastava for providing literatures, to Yi Yang for his assistance in fieldwork. We also thank two anonymous reviewers and the editor for their helpful and constructive comments.