Pistrix

The pistrix patrolled the Mediterranean in art if not in life. It was a sea monster of composite anatomy — the body of a whale or enormous fish, the forelegs of a dragon or dog, and a mouth lined with serrated teeth that gave it its name (pistrix from pristis, "saw"). Its tail coiled in elaborate spirals, often ending in flukes or fins.

Roman mosaics from North Africa, particularly from Tunisia and Libya, are the richest source of pistrix imagery. The creature appears in marine processions alongside hippocampi, tritons, and dolphins, but where those are graceful, the pistrix is menacing. Its jaws gape. Its eyes are fixed and predatory. It represents the hostile sea — the force that shipwrecks and drowns.

Virgil placed a pistrix among the sea creatures that escorted Neptune. Pliny catalogued it as a real marine animal, possibly the sawfish or the whale. The word pristis survived into modern zoology as the genus name for sawfish (Pristis pristis), one of the few mythological creatures to donate its name to its own probable inspiration.

In naval terminology, pristis was also used for a type of fast warship — the saw-toothed ram at its prow echoing the creature's jaws. To be attacked by a pristis, whether biological or nautical, meant being cut apart.

The pistrix occupied a specific ecological niche in Greek and Roman imagination: the large marine predator that you heard about but never saw, the shape beneath the hull that you hoped was a dolphin and feared was not.