A new fossil fern of the Dryopteridaceae (Polypodiales) from the mid-Cretaceous Kachin amber.

Dryopteridaceae are the basal family of Eupolypods I (Polypodiales) and include abundant extant species, but fossil occurrences are limited, particularly from a temporal perspective. Although DNA-based molecular studies indicate that the origin of Dryopteridaceae dates to the Early Cretaceous, no unambiguous fossil of the family has been reported from the Cretaceous period. Here, we report a new fern taxa based on well-preserved fertile specimen frond from mid-Cretaceous Kachin amber. Based on sporangia with interrupted, vertical annulae; monoletee spores; and the absence of indusia, the fertile fern fossil has been assigned to a new genus of Dryopteridaceae (Polypodiales). This represents the first fossil record of Dryopteridaceae from the Mesozoic and its mid-Cretaceous age is largely consistent with molecular-based estimates of divergence time. The fossil extends our understanding of polypod fern diversity in Mesozoic forests. [ABSTRACT FROM AUTHOR]