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