Fig. 3: RUNX2 QA repeat evolution throughout vertebrates.

Simplified phylogeny showing the evolution of the RUNX2 QA repeat during vertebrate history. Evolutionary relationships between major vertebrate radiations are shown with median divergence times. Representative species of each group are shown by silhouettes, and repeat structures with Q, spacer, and A residues are shown for each group on the right. The QA repeat emerged in the last common ancestor of gnathostomes and can be observed in all subsequent extant lineages. The repeat continued to expand throughout early tetrapods and amniotes, before reaching its long and variable modern condition in eutherian mammals <100 million years ago. Taxa silhouettes were created from images under a CC BY 4.0 open license.