• Source: Eugeneodontida

The Eugeneodontida, sometimes also called Eugeneodontiformes, is an extinct and poorly known order of cartilaginous fishes. They possessed "tooth-whorls" on the symphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lacked pelvic fins and anal fins. The palatoquadrate was either fused to the skull or reduced. Now determined to be within the Holocephali, their closest living relatives are chimaeras. The eugeneodonts are named after paleontologist Eugene S. Richardson, Jr. The group first appeared in the fossil record during the late Mississippian (Serpukhovian). The youngest eugeneodonts are known from the Early Triassic. The geologically youngest fossils of the group are known from the Sulphur Mountain Formation (western Canada), Vardebukta Formation (Svalbard, Norway) and Wordie Creek Formation (Greenland).
Members of the 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, Lestrodus, and Metaxyacanthus. All eugeneodonts are thought to have been obligate carnivores, with each genus having specialized feeding behaviors, territory ranges, and specific prey.
Among the eugeneodonts, some members of the superfamily Edestoidea are probably the largest marine animals of their time, with the Late Carboniferous Edestus estimated to reach about or exceeding 6.7 metres (22 ft) in length, with some Early Permian Helicoprion 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).




Taxonomy



The list below shows taxa included within Eugeneodontida.

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 Euctenius
Genus Prospiraxis
Genus Spiraxis
Genus Metaxyacanthus
Family incertae sedis
Genus Paredestus




References






External links


[1] Palaeos Vertebrates 70.100 Chondrichthyes: Eugnathostomata at paleos.com
JSTOR: Journal of Paleontology Vol. 70, No. 1 (Jan., 1996), pp. 162-165
More about Chondrichthyes Archived 2017-10-22 at the Wayback Machine at Devonian Times

Kata Kunci Pencarian:

• Helicoprion
• Holocephali
• Eugeneodontida
• Holocephali
• Fish
• Romerodus
• Actinopterygii
• Helicoprionidae
• Triassic
• Elasmobranchii
• Parahelicoprion
• Helicoprion