Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw.

[3] The unusual tooth arrangement is thought to have been an adaption for feeding on soft-bodied prey, and may have functioned as a deshelling mechanism for hard-bodied cephalopods such as nautiloids and ammonoids.

[2] Fossils of Helicoprion have been found worldwide, as the genus is known from Russia, Western Australia, China, Kazakhstan, Japan, Laos, Norway, Canada, Mexico, and the United States (Idaho, Nevada, Wyoming, Texas, Utah, and California).

[7][2] Almost all Helicoprion specimens are known solely from "tooth whorls", which consist of dozens of enameloid-covered teeth embedded within a common logarithmic spiral-shaped root.

The lowest portion of the root below the enameloid tooth projections is referred to as the "shaft", and lies on cartilage that encapsulates the previous revolutions of the whorl.

[3][9] Helicoprion had an autodiastylic jaw suspension, meaning that the inner edge of the palatoquadrate was firmly attached (but not fused) to the chondrocranium at two separate points.

By wedging into the palatoquadrate while the mouth is closed, the upper edge of the labial cartilage helps to spread out the forces used to limit the extent of the jaw closure.

[9] Ramsay and colleagues further suggested that the whorl could have served as an effective mechanism for deshelling hard-shelled cephalopods such as ammonoids and nautiloids, which were abundant in Early Permian oceans.

This system was effective at trapping and holding soft parts to increase cutting efficiency and provide leverage against hard-shelled prey.

This large bite force may have allowed Helicoprion to expand its diet to vertebrates, as its jaw apparatus was more than capable of cutting through skeletal elements of unarmoured bony fish and other chondrichthyans.

[9] Skull data from IMNH 37899 reveal several characteristics, such as an autodiastylic jaw suspension without an integrated hyomandibula, which confirm the placement of Helicoprion within the chondrichthyan subgroup Euchondrocephali.

Eugeneodonts have simple, autodiastylic skulls with reduced marginal dentition and enlarged whorls of blade-like symphysial teeth on the midline of the jaw.

[7] Three species of Helicoprion are currently considered valid via morphometric analyses, differing in the proportions of the upper, middle and lower sections of the tooth crown.

The first specimen of Helicoprion to be described was WAMAG 9080,[2] a 15-tooth fragment of a tooth whorl found along a tributary of the Gascoyne River in Western Australia.

[14] Karpinsky's identification of Edestus davisii as a species of Helicoprion would eventually be upheld by Curt Teichert, who described several more complete tooth whorls from the Wandagee Formation of Western Australia in the late 1930s.

[15] In 1907 and 1909, Oliver Perry Hay described a new genus and species of eugeneodont, Lissoprion ferrieri, from numerous fossils found in phosphate-rich Phosphoria Formation on the border between Idaho and Wyoming.

[17] H. ferrieri was initially differentiated using the metrics of tooth angle and height, but Tapanila and Pruitt (2013) considered these characteristics to be intraspecifically variable.

One of these, H, sierrensis, was described from a specimen (UNMMPC 1002) found in glacial moraine deposits in Eastern California, likely originating from the Goodhue Formation.

[2] One of two Helicoprion species described by Wheeler in 1939, H. nevadensis, is based on a single partial fossil found in a Nevadan mine by Elbert A. Stuart in 1929.

[2] Based on isolated teeth and partial whorls found on the island of Spitsbergen, Norway, H. svalis was described by Stanisław Siedlecki in 1970.

H. ergassaminon was named and described in detail within a 1966 monograph by Svend Erik Bendix-Almgreen,[8] and the holotype specimen ("Idaho 5"), bears breakage and wear marks indicative of its usage in feeding.

[12] Karpinsky's 1899 monograph on Helicoprion noted that the bizarre nature of the tooth whorl made reaching precise conclusions on its function difficult.

[28] Shortly after his original monograph, Karpinsky published the argument that the whorl represented a curled, scute-covered tail akin to that of Hippocampus (seahorses).

E. Van den Broeck noted the fragility of the structure and argued that it was most well-protected as a paired feeding apparatus in the cheek of the animal.

[31] G. Simoens illustrated Karpinsky's various proposals and used histological data to adamantly argue that the whorls were toothed structures placed within the mouth.

The utility of the tooth whorl in this type of reconstruction was inferred based on sawfish, which incapacitate prey using lateral blows of their denticle-covered snouts.

[8] In the 1994 book Planet Ocean: A Story of Life, the Sea, and Dancing to the Fossil Record, author Brad Matsen and artist Ray Troll describe and depict a reconstruction based on the information gleaned by Bendix-Almgreen (1966).

Designed under the direction of Robert Purdy, Victor Springer, and Matt Carrano, Parrish's reconstruction places the whorl deeper within the throat.

This hypothesis was justified by the argument that the teeth supposedly had no wear marks, and the assumption that the whorl would have created a drag-inducing bulge on the chin of the animal if located in a symphysial position.

[6] Lebedev's reconstruction approximates modern views on Helicoprion's anatomy, though the hypothetical long jaw and Campodus-like lateral dentition has been superseded by CT data.