Fig. (2) Cladistic relationships of the taxa covered in this study. Relationships are based on Janvier [34], Delarbre et al. [35] and the Tree of Life Web Project (www.tolweb.org), with informal names substituted for most groups. Nodes for which there is no general consensus are left unresolved (indicated by asterisks). Some taxa not mentioned in the study are omitted, e.g., caecilians. Two wholly extinct agnathan groups are included: basal jawless fishes, a diverse assemblage of primitive vertebrates, and cephalaspids.