Subclass Elasmobranchii Bonaparte, 1838 - shark-like fishes see Infraclass Elasmobranchii Bonaparte, 1838 Cohort Euselachii Hay, 1902 - spined sharks and relatives see Subclass Euselachii Hay, 1902 Subcohort Neoselachii Compagno, 1977 - modern sharks and rays see Infraclass Elasmobranchii Bonaparte, 1838 Order Heterodontiformes Compagno, 1973 - bullhead sharks 1 Family Heterodontidae Gray, 1851 - bullhead sharks