Fig. 1. Vascular plant phylogeny and occurrences of secondary vascular tissues (tree based on Kenrick and Crane, 1997 ; Rothwell, 1999 ). Gray rectangles represent paraphyletic grades. Fern clades 1–3 as defi ned by Rothwell (1999) : (1) Stauropteridales; (2) Zygopteridales + cladoxylopsids; and (3) living and extinct Filicales and Hydropteridales. Lineages with secondary vascular tissues arrowed, in red: the isoetalean clade (nested within the lycopsids);fern clade 2 with up to three distinct lineages (not shown) exhibiting secondary vascular tissues (cladoxylopsids, Zygopteridales, and Rhacophytales); sphenopsids; lignophytes; and basal euphyllophytes (asterisk), which now include three distinct plants with evidence for secondary xylem—two described by Gerrienne et al. (2011) and Franhueberia described here.