<==o CRYPTODIRA (pystytaivuttajat)
   |-- BAENOIDEA [paraphyletic??]
   `--o EUCRYPTODIRA
      |--o †Plesiochelyidae
      |  |-- †Craspedochelys
      |  |-- †Plesiochelys [Brodiechelys, Hylaeochelys, Parachelys, Tholemys, Wincania]
      |  |-- †Portlandemys
      |  `-- †Tienfuchelys
      `--+?- †Xinjiangchelys
         `--+--o †Sinemydidae
            |  |-- †Manchurochelys
            |  `-- †Sinemys
            `--o POLYCRYPTODIRA
               |-- Chelydridae (näykkijäkilpikonnat)
               `--o PROCOELOCRYPTODIRA
                  |--o "CHELONIMORPHA" [Chelonioidea sensu stricto]
                  |  |-- CHELONIOIDEA
                  |  `-- DERMOCHELYOIDEA
                  `--o CHELOMACRYPTODIRA
                     |-- TESTUDINOIDEA
                     `-- TRIONYCHOIDEA


Reference(s):

    Hirayama, R., 1997: Distribution and diversity of Cretaceous chelonioids. Chapter 8, pp. 225 - 243.
in Callaway,  J. M. & Nicholls, E. L., (eds.), 1997: Ancient marine reptiles.

–Academic Press, San Diego, 1997, pp. xlvi - 501

    Hirayama, R., 1998: Oldest known sea turtle.
–Nature: Vol. 392, 16 April, pp. 705-708

    Meylan, P. A. & Ganko, E., in prep.: Higher Relationships of Testunides - The extinct and living turtles.
–iNet: Tree of Life

    Meylan, P. A. & Ganko, E., in prep.: Polycryptodira - Living turtles other than side-neked turtles.
–iNet: Tree of Life