Clade Lepidosauria Haeckel 1866 [de Queiroz & Gauthier 2020] see Subclass Lepidosauria Duméril & Bibron, 1839
   Clade Rhynchocephalia Günther 1867 [Gauthier, Estes & de Queiroz 1988] see Order Rhynchocephalia Günther, 1867
     Clade Sphenodontia Williston 1925 [Evans 2003]
       Clade Acrosphenodontia Chambi-Trowell, Martinelli, Whiteside, Romo de Vivar, Soares, Schultz, Gill, Benton & Rayfield 2021
         Clade Eusphenodontia Herrera-Flores, Stubbs, Elsler & Benton 2018
           Clade Neosphenodontia Herrera-Flores, Stubbs, Elsler & Benton 2018
             Clade Sphenodontidae Cope 1871 [Simões, Caldwell & Pierce 2020] see Family Sphenodontidae Cope, 1871
               1 Genus Sphenodon Gray, 1831
               2 Genus †Cynosphenodon Reynoso, 1996
               3 Genus †Sphenovipera Reynoso, 2005
               4 Genus †Kawasphenodon Apesteguía, 2005
               5 Genus †Pelecymala Fraser, 1986
               6 Clade †Eilenodontinae Rasmussen & Callison 1981 [Simões, Caldwell & Pierce 2020] see Subfamily Eilenodontinae Rasmussen & Callison, 1981