Pteridaceae is a family of ferns in the orderPolypodiales, including some 1150 known species in ca 45 genera, divided over five subfamilies. The family includes four groups of genera that are sometimes recognized as separate families: the adiantoid, cheilanthoid, pteridoid, and hemionitidoid ferns. Relationships among these groups remain unclear, and although some recent genetic analyses of the Pteridales suggest that neither the family Pteridaceae nor the major groups within it are all monophyletic, as yet these analyses are insufficiently comprehensive and robust to provide good support for a revision of the order at the family level.
Description
Members of Pteridaceae have creeping or erect rhizomes. The leaves are almost always compound and have linear sori that are typically on the margins of the leaves and lack a true indusium, typically being protected by a false indusium formed from the reflexed margin of the leaf.
As traditionally defined, the groups within Pteridaceae are as follows:
Adiantoid ferns ; epipetric, terrestrial or epiphytic in moist habitats, rachis often dichotomously branching; sori relatively small and discrete with sporangia born on the false indusium rather than the leaf bladeproper; only one genus:
Cheilanthoid ferns; primarily epipetric in semiarid habitats; leaves mostly with well-developed scales or trichomes, often bipinnate or otherwise highly compound; sporangia mostly born in marginal sori with false indusia that are +/- continuous around the leaf margins; several genera, including:
Pteridoid ferns ; terrestrial and epipetric in moist habitats; leaves mostly without prominent scales or trichomes, most often pinnate but sometimes more compound; sporangia born in marginal sori with false indusia that are +/- continuous around the leaf margins; several genera, including:
* Pteris L. - brakes
* Onychium Kaulf.
Parkerioid ferns ; aquatic in swamps and/or mangroves, including:
* Acrostichum L. - leather ferns
* Ceratopteris Brongn.
Hemionitidoid ferns; terrestrial, epipetric or epiphytic in moist or semiarid habitats; leaves simple, pinnate, or more compound; sporangia born in linear non-marginal, exindusiate sori or sometimes in marginal sori; several genera, including:
* Anogramma Link
* Cryptogramma R.Br. - rock brakes
* Eriosorus Fée
* Hemionitis L.
* Jamesonia Hook. & Grev.
* Pityrogramma Link - gold ferns
Vittarioid ferns ; primarily epiphytic in tropical regions and all have simple leaves with sori that follow the veins and lack true indusia:
Based on phylogenetic research, Christenhusz et al. divided the Pteridaceae genera into five subfamilies. These roughly correspond with the groups listed above, with the main difference being that adiantoid and vittarioid ferns are combined under the Vittarioideae subfamily name. The approach was followed by the Pteridophyte Phylogeny Group classification of 2016.
