Eugeneodontiformes

The Eugeneodontiformes are an order of prehistoric cartilaginous fishes commonly known as the Eugeneodonts. They are renowned for having unique circular saw-like structures called tooth whorls on the symphysis of either the lower or both jaws. The palatoquadrate was either fused to the skull or reduced. Now belonging within the Holocephali, their closest living relatives are the chimaeras. They probably lacked pelvic and anal fins.

Some eugeneodonts in the superfamily Edestoidea were probably the biggest marine creatures of their time, with the famous Pennsylvanian Edestus estimated to reach about or exceed 6.7 metres (22 ft) in length, with some Helicoprion from the Cisuralian epoch suggested to be over 7.6 metres (25 ft) long, according to some estimates.

 Taxonomy 

 Superfamily Caseodontoidea
 Family Caseodontidae
 Genus Caseodus
 Genus Erikodus
 Genus Fadenia
 Genus Ornithoprion
 Genus Pirodus
 Genus Romerodus
 Family Eugeneodontidae
 Genus Bobbodus
 Genus Eugeneodus
 Genus Gilliodus
 Family incertae sedis
 Genus Campodus
 Genus Chiastodus
 Genus Tiaraju
 Superfamily Edestoidea
 Family Helicoprionidae
 Genus Agassizodus
 Genus Arpagodus
 Genus Campyloprion
 Genus Helicoprion
 Genus Parahelicoprion
 Genus Sarcoprion
 Genus Sinohelicoprion
 Genus Toxoprion
 Family Edestidae
 Genus Edestus
 Genus Helicampodus
 Genus Lestrodus
 Genus Parahelicampodus
 Genus Syntomodus
 Genus Protopirata
 Genus Prospiraxis
 Genus Spiraxis
 Genus Metaxyacanthus
 Family incertae sedis
 Genus Paredestus

 Some genera 

 Helicoprion 
Helicoprion is perhaps the most iconic eugeneodont. It is from the family Helicoprionidae and is known for its famous tooth whorls which are situated on the lower jaw. H. bessonowi is the first species of this genus to be described from complete tooth whorls, demonstrating that Helicoprion is distinct from Edestus.

 Edestus 
Edestus is another famous eugeneodont of the family Edestidae. Just like Helicoprion, it had tooth whorls. The largest species, E. heinrichi, is estimated to have reached greater than 6.7 m (22 ft) in length, around the size of the largest known great white shark, possibly making it the largest marine predator to have ever existed up to that point.

 Fadenia 
Fadenia was another type of eugenodont from the family Caseodontidae. It is known from the Carboniferous Period of Missouri (United States), Permian period of Greenland, and the Early Triassic epoch of British Columbia, Canada (Sulphur Mountain Formation).

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Category:Cartilaginous fish