Helicoprion

***Helicoprion*** is an extinct genus of shark-like cartilaginous fish.

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

Like all chondrichthyan taxa, _Helicoprion's_ skeleton was made of cartilage. Scientists know very little about what the skeleton looked like, because cartilage rarely fossilizes.

It was always assumed that the _Helicoprion_ was a shark, but in reality, it is more closely related to ratfish.

## Description

Because its skeleton was made of cartilage, the entire body of this fish disintegrated once it began to decay, unless preserved by exceptional circumstances. This can make it hard to draw illustrations of the full body appearance of _Helicoprion_.

The tooth was unusual-looking. It looked like a circular saw. The tooth is popularly known as a tooth whorl. The largest known _Helicoprion_ tooth whorl, specimen IMNH 49382 representing an unknown species, reached 56 cm (22 in) in diameter and 14 cm (5.5 in) in crown height, which would have belonged to an individual over 7.6 m (25 ft) in length.

Some types of Eugeneodont fish with preserved postcrania include the Pennsylvanian to Triassic sharks _Caseodus,_ _Fadenia,_ and _Romerodus._

### Tooth whorls

A tooth whorl is a structure found on _Helicoprion_. Almost all _Helicoprion_ specimens are known solely from tooth whorls. They consist of many enameloid-covered teeth. The youngest and first tooth at the center of the spiral, referred to as the "juvenile tooth arch", is hooked, but all other teeth are generally triangular in shape, laterally compressed and often serrated.

### Other material

Several large whorls are difficult to assign to any particular species group, _H. svalis_ among them. IMNH 14095, a specimen from Idaho, appears to be similar to _H. bessonowi_, but it has unique flange-like edges on the apices of its teeth. IMNH 49382, also from Idaho, has the largest known whorl diameter at 56 cm (22 in) for the outermost volution (the only one preserved), but it is incompletely preserved and still partially buried. _H. mexicanus_, named by F.K.G. Müllerreid in 1945, was supposedly distinguished by its tooth ornamentation.

## Species

- _Helicoprion bessonowi_ <small>Karpinsky, 1899</small> (type)
- _Helicoprion davisii_ <small>Woodward, 1886</small>
- _Helicoprion ergassaminon_ <small>Bendix-Almgreen, 1966</small>

### _H. bessonowi_

_H. bessonowi_ is perhaps the best-known species of this genus. It was not the first species of _Helicoprion_ to be described, but it is the first one to be described from complete tooth whorls, which reveals _Helicoprion_ is a distinct taxon from _Edestus_. As a result, _H. bessonowi_ serves as the type species for _Helicoprion_.

### _H. davisii_

The first specimen of this genus was discovered along a tributary of the Gascoyne River. Henry Woodward named it _Edestus davisii,_ commemorating the man who found it. Later, in 1899, Alexander Karpinsky reassigned it to the genus _Helicoprion_, and renamed it to _H. davisii_.

### _H. ergassaminon_

_H. ergassaminon_ is known from the Phosphoria Formation of Idaho, just like _H. davisii_, though it is comparatively much rarer. _H. ergassaminon_ was named and described in detail by Svend Erik Bendix-Almgreen.

### Earliest depictions

Hypotheses for the placement and identity of _Helicoprion_<nowiki/>'s tooth whorls were controversial from the moment it was discovered. Woodward (1886), who referred the first known _Helicoprion_ fossils to _Edestus_, discussed the various hypotheses concerning the nature of _Edestus_ fossils.

Karpinsky's hypothesis of the placement of the tooth whorl was putting it on the nose. Many people said that "the tooth whorl on the nose looks so weird." It now has its tooth whorl in its lower jaw.

### Later depictions

By the mid-20th century, the tooth whorl was usually depicted as being on the lower jaw. The utility of the tooth whorl in this type of reconstruction was inferred based on sawfish, which have the ability to incapacitate and slice through prey using lateral blows of their spiky snouts.

## In popular culture

_Helicoprion_ was a famous animal because it has been found in many websites. People have given it the name **buzzsaw shark**.

## Related pages

- Caseodus
- Edestus
- Fadenia
- Dracopristis