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
               Clade †Eilenodontinae Rasmussen & Callison 1981 [Simões, Caldwell & Pierce 2020] see Subfamily Eilenodontinae Rasmussen & Callison, 1981
                 1.1 Genus †Fraserosphenodon Herrera-Flores et al., 2018
                 1.2 Genus †Opisthias Gilmore, 1909
                 2.1 Genus †Eilenodon Rasmussen & Callison, 1981
                 2.2.1 Genus †Sphenotitan Martínez, Apaldetti, Colombi, Praderio, Fernandez, Santi Malnis, Correa, Abelin & Alcober, 2013
                 2.2.2.1 Genus †Toxolophosaurus Olson, 1960
                 2.2.2.2 Genus †Priosphenodon Apesteguia & Novas, 2003