Based on expression data obtained in snakes, it has been hypothesized that this peculiar “deregionalized” limbless anatomy results from a corresponding homogenization of mesodermal Hox expression domains along the primary axis (Cohn and Tickle, 1999).
In this study we set out to analyze Hox expression in detail, including previously unexamined posterior paralog members in the corn snake (Pantherophis guttatus) and to a lesser extent, because of material scarcity, in a caecilian amphibian (Ichthyophis cf. kohtaoensis), which evolved a comparable body plan independently.