Figure 1. Hypothesis of relationships of major vertebrate groups with their most commonly agreed upon sister taxa. Not all hierarchical levels of vertebrate taxa are represented; rather, major vertebrate classes are included with representatives of their most commonly accepted sister taxa.

Figure 2. Representative transitional vertebrate taxa. (a) the ichthyostegid amphibian Acanthostega. (b) the ichthyostegid amphibian Ichthyosetga. (c) and (d) dorsal and occipital views of the high-fibre herbivore and near amniote Diadectes. The element indicated in red is the parietal bone (P). (e) and (f) right lateral and dorsal views of the advanced therapsid Morganucodon. (g) reconstruction of feathered juvenile dromaeosaurid dinosaur Sinornithosaurus. (a) and (b) after Lombard and Sumida (1992); (e) and (f) adapted from Benton (2005); (g) used with permission of the artist.