Ischyodus, Chimaera, Callorhinchidae, Cretolamna, Holocephali
Edaphodon was a prehistoric chimaeriform fish genus belonging to the family Callorhinchidae (sometimes assigned to Edaphodontidae). So, Edaphodon was a type of rabbitfish, a cartilaginous fish related to sharks and rays. Edaphodon has under 15 known species, all of which are extinct. This genus appeared in Aptian age (end of lower Cretaceous) and vanished in Pliocene. It was most prominent during the Late Cretaceous. All Edaphodon species were situated in the Northern Hemisphere, apart from E. kawai, which was recently discovered in the Chatham Islands near New Zealand. This shows the range of Edaphodon reached further than was previously thought.
Like most other Chimaeriformes, Edaphodon is known mainly from poorly preserved specimens; this because Edaphodon belongs to Chondrichthyes class, whose skeletons are made of cartilage. So, in most cases, only tooth plates and fin spines are preserved.
Edaphodon is similar to other rabbit fishes in appearance. Like other chimaeriforms, it fed using six tooth plates (one pair on the lower jaw and two pairs on the upper). Probably, it laid eggs in a leathery pouch like other rabbit fish, but no occurrences of this have been recorded. Edaphodon had a sloping head and a mouth on its underside, allowing it to graze along the bottom of the ocean like a land-dwelling herbivore, but actually it was feeding on small benthic animals.
The closest relative of Edaphodon was Ischyodus. A possibility exists that remains known as E. kawai actually belong to Ischyodus.
Edaphodon has numerous species, all of which are extinct: