Bivalvia Linnaeus, 1758 - bivalves
   Autobranchia Grobben, 1894
     Heteroconchia Gray, 1854
       Heterodonta Neumayr, 1884
         †"Megalodonts"
           1 †Congeriomorphidae Saul, 1976
           2 †Dicerocardiidae Kutassy, 1934
           3 †Mecynodontidae Haffer, 1959
           4 †Megalodontidae Morris & Lycett, 1853
           5 †Pachyrismatidae Scarlato & Starobogatov, 1979
           6 †Plethocardiidae Scarlato & Starobogatov, 1979
           7 †Wallowaconchidae Yancey & Stanley, 1999