The sandfish lizard spends most of its life buried in the sand—emerging only to eat, poop, and mate. This lifestyle helps the lizard evade the sweltering desert heat in the Middle East and North Africa, but it causes another problem: inhaling sand particles. Yet when scientists looked into the respiratory tract and lungs of five dead lizards, they couldn’t find a single grain of sand. They couldn’t find an obvious filter in the lizard’s respiratory system, either.

Puzzled? So were the scientists. To know how they solved the mystery, go to Science.

Photo credit: Anna T. Stadler