Progressing distally from the root, Psilophyton crenulatum, the most basal clade, comprises the psilotophytes Psilotum + Tmesipteris, followed by the equisetophyte Equisetum, the seed plant Pinus, the ophioglossalean ferns Ophioglossum + Botrychium, the marattiaceous ferns Marattia + Angiopteris, and the "leptosporangiate" clade that consists of the Filicales + the Hydropteridales [ILLUSTRATION FOR FIGURE 4 OMITTED].
As in the complete analysis, the "leptosporangiate" clade is monophyletic and includes a paraphyletic Filicales and a monophyletic Hydropteridales [ILLUSTRATION FOR FIGURE 4 OMITTED].
Although more completely resolved at the base than comparable regions of the consensus tree for the complete analysis [ILLUSTRATION FOR FIGURE 2 OMITTED], decay index values suggest that the nodes in the "basal" Filicales and "derived" Filicales regions of the "extant only" tree are not strongly supported [ILLUSTRATION FOR FIGURE 4 OMITTED].
Likewise, placement of Marattiales in the current results [ILLUSTRATION FOR FIGURES 2 & 4 OMITTED] as sister group to the leptosporangiate Filicales + Hydropteridales agrees with traditional systematic interpretations (Gifford & Foster, 1989).
Shoot organization in the Filicales: The promeristem.
DNA microspectrophotometry of shoot apical meristem cell populations in Ceratopteris thalictroides (Filicales).
The developmental anatomy of Metaxya rostrata (Filicales: Metaxyaceae).
Organization of the vascular system in the stems of Diplazium and Blechnum (Filicales).
