If you spotted this bizarre object lying among the waves, your first reaction might be that something had escaped from a horror movie. Its twisted shape can resemble a shredded jaw, broken machinery, or even part of some strange creature. Beachgoers who discovered similar objects have taken photographs and wondered whether they were looking at a monster or an unusual mutation.

The truth, however, is far more fascinating. The strange structure is actually the hidden underside of a chiton, a small marine mollusk that lives attached to rocks along rough coastlines. From above, chitons look relatively ordinary, with eight overlapping plates protecting their bodies. But underneath those plates is a muscular foot surrounded by structures that can look remarkably similar to rows of teeth.