Helicoprion was a prehistoric shark-like fish that lived during the Late Permian period, around 290 to 250 million years ago. Notable for its unique and distinctive spiral-toothed jaw, Helicoprion had teeth arranged in a whorl-like pattern, resembling a circular saw. This unique feature is thought to have been used for slicing through prey, including cephalopods and fish. Measuring up to 8 meters (26 feet) in length, Helicoprion was an apex predator of its time. Fossils, primarily consisting of its teeth, have been found in various locations including Russia and the United States, providing important insights into the evolution of ancient predatory fish.