Parahelicoprion

Parahelicoprion is an extinct genus of shark-like cartilaginous fish that lived during the Early Permian. The genus contains two species: P. clerci from the Arta Beds of the Ural Mountains of Russia, and P. mariosuarezi from the Copacabana Formation of Bolivia. Members of the genus possessed a row of large tooth crowns on the midline of the lower jaw, known as a tooth whorl. The characteristics of this whorl are unique to fishes of the order Eugeneodontida, and more specifically the family Helicoprionidae to which Parahelicoprion belongs. The genus name refers to Helicoprion, another eugeneodont from the Ural Mountains that bore a similar midline tooth arrangement.

The holotype of Parahelicoprion clerci, which consists only of tooth fragments, was badly damaged by mining and is broken into several pieces. That of the Bolivian P. mariosuarezi similarly consists of only nine partial teeth, the outer edges of all of which are broken off. Estimates of the extent of the complete whorl, body size, and ecology of Parahelicoprion are speculative as a result of its incomplete fossils, although it is assumed to have been very large, predatory, and potentially pelagic. When first described, P. clerci was considered a species of Helicoprion, although its initial describer, Alexander Karpinsky, later separated it into its own genus. It has since been suggested that this genus may indeed represent a junior synonym of Helicoprion or a paraphyletic, non-diagnostic taxon.