Figure 2.

Strict consensus of two most parsimonious trees of phylogenetic relationships between the pterygotid eurypterids and their immediate sister-taxa plotted on a stratigraphic column with bootstrap values based on 100 000 repetitions indicated at individual nodes. Estimated maximum size of individual taxa indicated in parentheses. Unequivocal synapomorphies at the numbered nodes are listed in the electronic supplementary material. Stratigraphic Series: We, Wenlock; Lu, Ludlow; P, Pridoli; Lo, Llandovery; Pra, Pragian; Ems, Emsian; Eifel, Eifelian.