What is Helicoprion?
[[File:Helicoprion bessonovi1DB.jpg|thumb|Artist's reconstruction]] '''''Helicoprion''''' is an extinct genus of [[Chondrichthyes|cartilaginous fish]]. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called [[Tooth whorl|tooth whorls]], which in life were embedded in the lower jaw. As with most extinct [[Chondrichthyes|cartilaginous fish]], the skeleton is mostly unknown. It is one of the most popular [[Shark|sharks]] of all time. It was always assumed that the ''Helicoprion'' was a shark, but it is more closely related to [[Chimaera (fish)|ratfish]]. == Description == It had skeletons made of cartilage. As a result, the entire body disintegrated once it began to decay, unless preserved by exceptional circumstances. This can make it difficult to draw precise conclusions on the full body appearance of ''Helicoprion''. The tooth was unusual-looking. Many shark fans call the tooth 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. === Tooth whorls === {{main|Tooth whorl}} A '''[[tooth whorl]]''' is a structure found on the ''Helicoprion''. Almost all ''Helicoprion'' specimens are known solely from [[Tooth whorl|tooth whorls]], which is a name shark lovers call when they see a [[tooth whorl]]. == Species == * ''[[Helicoprion bessonowi]]'' <small>Karpinsky, 1899</small> (type) * ''[[Helicoprion davisii]]'' <small>Woodward, 1886</small> * ''[[Helicoprion ergassaminon]]'' <small>Bendix-Almgreen, 1966</small> == 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 outerm