Palaeobiogeographical implications of the earliest botryopterid ferns in Cathaysia

ABSTRACT

The Wuda Tuff Flora from the Taiyuan Formation of Inner Mongolia is a palaeobotanical lagerstätte that is key to our current understanding of the composition and ecology of the earliest Permian Cathaysian floras. We investigate an anatomically preserved axis that represents an additional plant family recorded in this flora and considers its palaeobiogeographical implications. The specimen possesses an ω-shaped vascular strand and has features that conform to the botryopterid fern Botryopteris. Comparisons indicate greatest similarity with Botryopteris scottii from the Pennsylvanian of England but due to limited information we assign it to Botryopteris cf. scottii. The new finding represents the earliest stratigraphic occurrence of botryopterids in the Cathaysian floras. Alongside Botryopteris tridentata and Botryopteris cf. forensis in slightly younger Cisuralian strata from China, it demonstrates migration of closely related species from the Pennsylvanian wetlands of Euramerica into the Permian wetlands of Cathaysia. Together with unexpectedly early stratigraphic occurrences of the ‘Methuselah taxa’ Yuania, Gigantonoclea and Autunia in the roof shale flora of the coal seam overlying the Wuda Tuff Flora, B. cf. scottii adds to a growing body of evidence that records significant floral interchange and migration from different ecological settings in the Cathaysian and Euramerican floras by the earliest Permian.

KEYWORDS:

• Wuda Tuff Flora
• Botryopteris
• palaeobiogeography
• Cathaysia
• Euramerica
• migration

Acknowledgments

We are grateful to several technicians of NIGPAS for their help including Mr Sheng-Wu Mei for the fieldwork assistance, Mr You-Dong Chen and Mr Yang Gao for the rock sectioning and polishing, and Mrs Jing-Jing Tang for assistance with microscopy.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the National Natural Science Foundation of China [41802011, 41872013, 41530101]; the Strategic Priority Research Program (B) of Chinese Academy of Sciences [XDB18000000, XDB26000000]; and the State Key Laboratory of Palaeobiology and Stratigraphy (NIGP) [20182114]. The authors are very grateful to the Grant Agency of the Czech Republic for the financial support that covered part of this research related to data processing via the grant project GA19-06728S. Part of this contribution was also supported by the Research Program of West Bohemian Museum in Pilsen [DKRVOZCM2020-25/92P].