New information and family relationship (Hymenophyllaceae) for the fossil fern genus Acrostichopteris Fontaine and a new species from the Lower Cretaceous (Albian) of Spain.

Assignment of this fossil to the family Hymenophyllaceae is based on all characters known and comparison to modern species, provides the time for appearance of characteristics within the family, and indicates diversification of Hymenophyllum species in the mid-Cretaceous.