This figure comes from Rothwell (1999) and analyzes representatives of all vascular cryptogam groups. Of the terminal taxa, 26 are extant and 26 are extinct. The taxa are compared on the basis of 101 morphological characters. Rothwell interprets the figure to represent 3 clades of ferns, 2 of which are entirely extinct. In this figure, the psilophytes are the sister group to all other extant vascular plants. Also, the the clade that includes the horsetails (Equisetophytes) is sister to the clade of seed plants. This is similar to the phylogenies proposed by Pearson (1995; see vascular plant origin and the relationships among the ferns). Note the differences between this figure and Pryer et al. (2001).