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Eugeneodontida is an extinct and poorly known order of bizarre cartilaginous fishes. They possessed a unique "tooth-whorl" on the symphysis of the lower jaw as well as pectoral fins supported by long radials. The palatoquadrate was either fused to the skull or reduced. Now determined to be within Holocephali, their closest living relatives are ratfish.〔 The meaning of the name ''Eugeneodont'' correlates to "true origin teeth", and comes from the Greek words ''eu'' (good/true), ''geneos''(race, kind, origin) and ''odon (tooth.)'' Members of Eugeneodontida are further classified into different families, the most well-preserved members that have been discovered are commonly placed within the families Helicoprionidae ("Spiral Saws"), and Edestidae ("Those which Devour"), the former containing the genera ''Helicoprion'', ''Sarcoprion'' and ''Parahelicoprion'', and the latter containing the genera ''Edestus'', ''Listracanthus'' and ''Metaxyacanthus''. All eugeneodonts are thought to be obligate carnivores, with each genera having specialized feeding behaviors, territory ranges and specific prey. ==Taxonomy== * *Family Caseodontidae * * *Genus ''Caseodus'' * * *Genus ''Erikodus'' * * *Genus ''Fadenia'' * * *Genus ''Ornithoprion'' * * *Genus ''Romerodus'' * *Family Eugeneodontidae * * *Genus ''Bobbodus'' * * *Genus ''Eugeneodus'' * * *Genus ''Gilliodus'' *Superfamily Edestoidea * *Family Helicoprionidae * * *Genus ''Agassizodus'' * * *Genus ''Arpagodus'' * * *Genus ''Campyloprion'' * * *Genus ''Helicoprion'' * * *Genus ''Parahelicoprion'' * * *Genus ''Sarcoprion'' * * *Genus ''Toxoprion'' * *Family Edestidae * * *Genus ''Edestus'' * * *Genus ''Helicampodus'' * * *Genus ''Listracanthus'' * * *Genus ''Lestrodus'' * * *Genus ''Metaxyacanthus'' * * *Genus ''Parahelicampodus'' * * *Genus ''Physonemus'' * * *Genus ''Prospiraxis'' * * *Genus ''Syntomodus'' *Superfamily Caseodontoidea (Family unknown) * *Genus ''Campodus'' * *Genus ''Chiastodus'' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「eugeneodontida」の詳細全文を読む スポンサード リンク
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