Tiliqua gigas is thought to be most closely related to T. scincoides, the better-known Australian blue-tongued skink, but the two possess different color patterns. Tiliqua scincoides is light in color, or at least possesses both dark and light cross-stripes, whereas T. gigas has dark flanks, tending toward black, with at most vaguely present stripes (Gorseman 1998).