Class [Reptilia] Linnaeus, 1758 - reptiles
   Subclass Lepidosauria Duméril & Bibron, 1839
     Order Rhynchocephalia Günther, 1867 - tuataras
       Suborder Sphenodontoidea Lydekker, 1888
         1 Family †Polysphenodontidae Kuhn, 1969 [monotypic]
         2 Family Sphenodontidae Cope, 1871 - tuataras
         3 Family †Palacrodontidae Haughton, 1924 [monotypic] see Family Sphenodontidae Cope, 1871
         4 Family †Monjurosuchidae Endo, 1940 see Family Sphenodontidae Cope, 1871