| Eugeneodontiformes | |
|---|---|
 | |
| Helicoprion davisii | |
 | |
| Edestus heinrichi | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | †Euchondrocephali |
| Order: | †Eugeneodontiformes Zangerl, 1981 |
| Families | |
See text | |
| Synonyms | |
| |
Eugeneodontiformes (also calledEugeneodontida) is anextinct and poorly knownorder ofcartilaginous fishes. They possessed "tooth-whorls" on thesymphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lackedpelvic fins and anal fins.[1] Thepalatoquadrate was either fused to the skull or reduced. They are now determined to be within theHolocephali; their closest living relatives arechimaeras.[2] The eugeneodonts are named after paleontologistEugene S. Richardson, Jr.[3] The group first appeared in the fossil record during the lateMississippian (Serpukhovian).[4] The youngest eugeneodonts are known from theEarly Triassic.[5] The geologically youngest fossils of the group are known from theSulphur Mountain Formation (western Canada),Vardebukta Formation (Svalbard, Norway) andWordie Creek Formation (Greenland).
Members of the Eugeneodontiformes are further classified into two superfamilies and either four or five different families. TheHelicoprionidae andEdestidae are assigned to the superfamilyEdestoidea, the former containing genera such asHelicoprion,Sarcoprion, andParahelicoprion, and the latter containing the genera such asEdestus andLestrodus. The family Helicampodontidae has been used for genera that do not closely resemble typical members of either of these two groups.[6] The superfamilyEugeneodontoidei (traditionallyCaseodontoidea)[7] includes the familiesCaseodontidae andEugeneodontidae, which were smaller and less-specialized than the edestoids.[3] Eugeneodonts were predatory, with eugeneodontoids likely being generalist feeders and some edestoids being specialized for huntingcephalopods.[1][3][8]
Among the eugeneodonts, some members of the superfamily Edestoidea are probably the largest marine animals of their time, with theLate CarboniferousEdestus estimated to reach about or exceeding 6.7 metres (22 ft) in length,[9][10] with someEarly PermianHelicoprion suggested to be over 7.6 metres (25 ft) long by some estimates (though the body length estimates for both genera are somewhat speculative due to both only being known from skull material).[9][10][8]
The list below showstaxa included within Eugeneodontiformes.[11]
| Forerunners | 
| ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Jawless fish |
| ||||||||||||
| Jawed fish |
| ||||||||||||
| Lists | |||||||||||||
| Related | |||||||||||||
† extinct | |||||||||||||
 | This article about aprehistoriccartilaginous fish is astub. You can help Wikipedia byexpanding it. |
.png)