Clade Lepidosauria Haeckel 1866 [de Queiroz & Gauthier 2020] see Subclass Lepidosauria Duméril & Bibron, 1839
Count: [*†*] 2g;1s; †34g;42s
   Clade Rhynchocephalia Günther 1867 [Gauthier, Estes & de Queiroz 1988] see Order Rhynchocephalia Günther, 1867
  Count: [*†*] 1g;1s; †30g;38s
     Clade Sphenodontia Williston 1925 [Evans 2003]
    Count: [*†*] 1g;1s; †29g;37s
       Clade Acrosphenodontia Chambi-Trowell, Martinelli, Whiteside, Romo de Vivar, Soares, Schultz, Gill, Benton & Rayfield 2021
      Count: [*†*] 1g;1s; †28g;36s
         Clade Eusphenodontia Herrera-Flores, Stubbs, Elsler & Benton 2018
        Count: [*†*] 1g;1s; †24g;32s
           Clade Neosphenodontia Herrera-Flores, Stubbs, Elsler & Benton 2018
          Count: [*†*] 1g;1s; †21g;24s
             Clade Sphenodontidae Cope 1871 [Simões, Caldwell & Pierce 2020] see Family Sphenodontidae Cope, 1871
            Count: [*†*] 1g;1s; †10g;11s
               Genus †Sphenovipera Reynoso, 2005
              Count: [†*] †1s
                 1 †Sphenovipera jimmysjoyi Reynoso, 2005
                Count: -