What is "helicoprion"

Helicoprion is a long-lived genus of extinct, shark-like eugeneodontid holocephalid fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls." Helicoprion first arose in the oceans of the early Permian , survived the Permian–Triassic extinction event, and eventually became extinct during the Early Triassic, . Its name is Greek for "spiral saw". The closest living relatives of Helicoprion (and other eugeneodontids) are the chimaeras.