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 †Clevosauridae Fraser 1993 [Bonaparte & Sues 2006] see Family Clevosauridae Fraser, 1993
             Genus †Clevosaurus Swinton, 1939
               1.1 †Clevosaurus convallis Säilä, 2005
               1.2.1 †Clevosaurus brasiliensis Bonaparte & Sues, 2006
               1.2.2 †Clevosaurus hadroprodon Hsiou et al., 2019
               2.1 †Clevosaurus bairdi Sues et al., 1994
               2.2.1 †Clevosaurus hudsoni Swinton, 1939
               2.2.2 †Clevosaurus cambrica Keeble et al., 2018