Across the vast, hyper-arid dune seas of the western Sahara, surface temperatures routinely climb past 60 degrees Celsius by midday. Solar radiation bakes the fine quartz sediment into a treacherous, shifting furnace that drives most endemic desert wildlife deep into subterranean burrows until nightfall. Yet amid the scorching winds of Morocco’s Erg Chebbi, a small, polished reptile executes an evolutionary feat unmatched by almost any other terrestrial vertebrate: it plunges headfirst into the vertical slope of a sand dune and disappears into the substrate, moving through solid ground with the fluid grace of a fish in open water. This is the Saharan sandfish lizard ( Scincus scincus ), a specialized skink whose extraordinary biological adaptations have made it the focus of recent biomechanical and sensory research. Rather than scrambling across the loose, unstable surface, the sandfish utilizes the subsurface dune layer as...