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).
4-658: 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
8-535: A prehistoric holocephalan is a stub . You can help Misplaced Pages by expanding it . Helicoprionidae Helicoprionidae (sometimes referred to as Agassizodontidae ) is an extinct family of holocephalans within the order Eugeneodontida . Members of the Helicoprionidae possessed a "whorl" of tooth crowns connected by a single root along the midline of the lower jaw . While historically considered elasmobranchs related sharks and rays ,
12-428: The closest living relatives of the Helicoprionidae and all other eugeneodonts are now thought to be the ratfishes . The anatomy of the tooth-whorls vary between taxa, with some possessing highly specialized, coiling spirals (such as those of the namesake genus Helicoprion ), while others such as Sarcoprion and Parahelicoprion possessed shorter whorls . This article about a prehistoric holocephalan
16-753: 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). The list below shows taxa included within Eugeneodontida. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] This article about
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