A fossil species of the enigmatic early polypod fern genus Cystodium (Cystodiaceae) in Cretaceous amber from Myanmar

Ledis Regalado,Jochen Heinrichs,Bork Ilsemann,Harald Schneider,Michael Krings,Alexander R Schmidt,Marc S Appelhans

doi:10.1038/s41598-017-14985-7

Abstract

The monospecific fern genus Cystodium (Cystodiaceae; Polypodiales) occurs exclusively in the tropical forests of the Malay Archipelago, the Admiralty Islands, the Louisiade Archipelago, and the Solomon Islands. Divergence time estimates suggest that the genus originated in the Mesozoic; however, fossil evidence to validate this suggestion has been lacking. Amber from Myanmar (Burmese amber) is an important source of new information on the diversity of vascular cryptogams in the Cretaceous. This paper describes the fossil taxon Cystodium sorbifolioides nov. sp. based on a fragment of a fertile leaf preserved in Burmese amber that represents the first fossil evidence of the family Cystodiaceae. Cystodium sorbifolioides is used to obtain a minimum age estimate for the Cystodiaceae and the closely related, monogeneric Lonchitidaceae and Lindsaeaceae. The fossil strengthens the hypothesis that the forest ecosystems of Malesia and Melanesia represent refugia for many tropical plant lineages that originated in the Cretaceous.

Highlights

The monospecific fern genus Cystodium (Cystodiaceae; Polypodiales) occurs exclusively in the tropical forests of the Malay Archipelago, the Admiralty Islands, the Louisiade Archipelago, and the Solomon Islands
Fossils of fern foliage[20,21,22,23] exquisitely preserved in mid-Cretaceous amber from Myanmar[24,25,26,27] have become increasingly important as a source of new information on Cretaceous fern diversity and have contributed greatly to the resolution of several striking discrepancies between the age estimates obtained by molecular dating and the minimum ages of lineages provided by the fossil record, for instance with regard to the crown group Dennstaedtiaceae Lotsy[21]
We describe the fossil taxon Cystodium sorbifolioides nov. sp. based on a fragment of a fertile leaf preserved in Burmese amber

Summary

Introduction

The monospecific fern genus Cystodium (Cystodiaceae; Polypodiales) occurs exclusively in the tropical forests of the Malay Archipelago, the Admiralty Islands, the Louisiade Archipelago, and the Solomon Islands. The newly described fossil is used to obtain a minimum age estimate for the fern family Cystodiaceae, as well as for the closely related Lonchitidaceae and Lindsaeaceae.

Results

Conclusion