Based on skull structure, the genus Gongylophis Wagler is again placed in synonomy with the genus Eryx Daudin. Lichanura is considered to be structurally close to the early erycine stock from which Charina evolved as an early, separate off-shoot.
Skull characters which adapt erycines to burrowing habits show clinal variation: they involve shortening of the skull and streamlining of its contours through snout depression, the development of a spatulate transverse process of the pre-maxilla reinforced by the nasals and a specialization of the naso-frontal joint which supports the snout. The jaws retain their mobility. Burrowing habits are a specialized feature of the Erycinae.