The Helicoprion Mystery

Picture Helicoprion: a school-bus-sized prehistoric fish with a "sawblade” of spiraling teeth…

…on its tail?

What in the whorl is that?

The 270-million-year-old tooth whorl of the “buzzsaw shark” Helicoprion (heel-uh-co-PRY-on) mystified scientists for decades. The rest of this ancient ratfish’s skeleton was made of soft cartilage, which decomposed and vanished, leaving only a fossilized spiral of spiky teeth. But what part of the fish was it, and what was it for? Scientists proposed — and hotly debated — every possibility, from nose to tail (the illustrations above were all based on actual theories).

In 2013, X-ray CT scans of a uniquely well-preserved fossil finally revealed that the “buzzsaw” whorl anchored to the lower jaw and sliced cutting-board-style against a smooth upper palate with hundreds of pounds of force. Only the most mature teeth were exposed; the whorl never stopped growing, with “baby teeth” being moved into the center of the whorl by the larger, newer teeth. The largest Helicoprion tooth whorl on record contains over 125 teeth and suggests a body length of 30–40 feet, making this enigmatic sea creature one of the biggest — and most horror-movie-ready — fish in evolutionary history.