Hypothetical scheme of the expansion of the Dlx genes in the cyclostome lineage. The right- and left-pointing boxed arrows represent the Dlx1/4/6 and −2/3/5 clade genes. Red and blue boxed arrows indicate the Dlx genes, showing the overlapping expression patterns in the inner ear and cranial ectomesenchymal cells, respectively. The grey area shows the species tree of the hagfish and lampreys. Black arrows indicate the evolutionary processes of the Dlx genes. The pseudogene and its evolutionary process are indicated by a white arrow and dotted line, respectively.
Fujimoto et al. BMC Evolutionary Biology 2013 13:15 doi:10.1186/1471-2148-13-15