Eugeneodontiformes

right|thumb|Helicoprion bessonovi, teeth at the front of the lower jaw (reversed for more natural position) 225px|thumb|Restoration of Romerodus ([[Caseodontidae)]]

Eugeneodontiformes (also called Eugeneodontida) 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. They are 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).