†family Helodontidae (chimaera)
Chondrichthyes - Helodontiformes - Helodontidae
Parent taxon: Helodontiformes according to J. S. Nelson 2006
See also Zangerl 1981
Sister taxa: none
Subtaxa: Helodus
Ecology: nektobenthic carnivore
Distribution:
• Permian of Australia (1 collection), Greenland (1), Lithuania (1), United States (11: Oklahoma, Wyoming)
• Carboniferous of Canada (1: Alberta), Ukraine (1), the United Kingdom (7), United States (4: Arizona, Illinois, Indiana, Nebraska)
• Devonian of Australia (1)
Total: 28 collections including 33 occurrences