Evolutionary scenario for the expression of <i>Dlx</i> genes in developing paired sensory placodes (A) and vesicles (B).

<p>The blue circle represents the hypothetical apparition of <i>Dlx</i> expression in this structure and blue cross indicates loss of expression for both <i>Dlx</i> genes of a cluster. A tilted bar indicates when only one gene of a cluster has lost expression in his structure. Genes for which expression is known to be positive are written black while genes for which no expression has been recorded are indicated in grey.