Gleicheniales

These ferns are characterized by root steles having 3–5 protoxylem poles and antheridia with 6–12 narrow, twisted or curved cells in their walls.

In the molecular phylogenetic classification of Smith et al. in 2006, the Gleicheniales were placed in class Polypodiopsida (the leptosporangiate ferns).

[1] The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009)[2] which placed all land plants in Equisetopsida,[3] reclassified Smith's Polypodiopsida as subclass Polypodiidae and placed the Gleicheniales there.

The oldest unambiguous records, belonging to the family Gleicheniaceae, are known from the Wuda Tuff flora of China, dating to the Asselian, approximately 298.34 million years ago.

The resultant group was treated as class Gleichenopsida alongside the Pteridopsida, which would then be limited to the leptosporangiate ferns.