The advent of modern morphogenetics has made it possible to reveal genetic positional markers that provide a fixed identity for each of the various skull components. The hyoid bone (Hy) played a key roll in the development of the ideas of unity of body plan (Geoffroy) and homology (Owen). It is specified by Hox a2, Hox b2, and Dlx 1&2, Dlx 5&6 and Dlx 3&7 genes as shown where the grid lines intersect in part B of the figure.