Parahelicoprion

Parahelicoprion is an extinct genus of shark-like eugeneodontid holocephalids from the Permian of the Ural Mountains and Copacabana Formation, Bolivia. The genus name, from "nearly coiled saw" in Greek, directly refers to "Helicoprion", a related holocephalid that shares similar traits to it, including the helical whorl of teeth.
Description.
One of the primary qualities that separate "Parahelicoprion" from "Helicoprion" is the shape, thickness, and angle of the tooth whorl. Its teeth protrude outwards not like a tightly coiled saw, but instead a curved arrangement of cutting blades indicating it relied less on crushing slow-moving invertebrates and catching cephalopods, or other small mollusk prey, but inflicting traumatic damage against more durable, faster prey. Their teeth grew at a much slower pace than those of other whorl-tooth sharks, resulting in a depreciated spiral, growing only half of the teeth a "Helicoprion" would grow in its lifetime. The tooth spiral also was able to indicate the age of the eugeneodontidans in question.
"Parahelicoprion" is estimated to have grown to lengths of around 12 m. It was once thought to be the largest of its family; in 2013, however, a tooth whorl of a large "Helicoprion" was described, indicating that the genus could grow to larger sizes. The fossils of "Parahelicoprion" indicate an animal that was overall more slender and less heavy than "Helicoprion" despite being comparably sized.
Paleobiology.
"Parahelicoprion" is thought to have been a nektonic carnivore that probably preyed upon a variety of different species, using its blade-like teeth to cut at exposed flesh like a hatchet or wedge.