After Moody, 1997, Hooks, 1998

<==o †Protostegidae Cope, 1872 sensu Moody, 1997 and Hooks, 1998
   |--o †Chelospharginae Zangerl, 1953
   |  `-- †Chelosphargis advena (Hay, 1906) Zangerl, 1953 [Protostega advena Hay, 1906]; U. Cret. NA. EAs. NZ.
   `--o †Protosteginae Zangerl, 1953
      |--o †Calcarichthyini Hook, 1998
      |  `-- †Calcarichelys gemma Zangerl, 1953; U. Cret. NA.
      `--o †Protostegini Hook, 1998
         |?- †“Protostega” anglica Lydekker, 1889 [?Chelone jessoni Lydekker, 1889] Cret. WEu.
         |--o †Microstegina Hook, 1998
         |  `-- †Microstega copei (Wieland, 1909) Hook, 1998 [Archelon copei Wieland, 1909 (in partim); “Protostega” copei (Wieland, 1909) Hirayama, 1998] U. Cret. NA.
         `--+?- †Atlantochelys mortoni Agassiz, 1849 [?Pneumatoarthrus peloreus Cope, 1870]; U. Cret. NA.
            `--o †Protostegina Hook, 1998
               |-- †Protostega gigas Cope, 1872; U. Cret. NA. EAs. [taxonomic history]
               `-- †Archelon ischyros Wieland, 1896 [Archelon marshi Wieland, 1900]; U. Cret. NA.

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