After Holmes, Carroll & Reisz, 1998, and Yates & Warren, 2000

<==o †Eryopoidea
   |--o †Zatracheidae
   |  |--o †Dasyceps Huxley, 1859
   |  |  |-- †D. bucklandii (Lloyd, 1850) [Labyrinthodon Bucklandi Lloyd, 1850]
   |  |  `-- †D. microphthalmus (Cope, 1896)
   |  |--o †Stegops Moodie, 1909
   |  |  |-- S. divaricata (Cope, 1885) Moodie, 1909 [Ceraterpeton divaricatum Cope, 1885; Erpetosaurus tuberculatus Moodie, 1907]
   |  |  |-- †S. newberryi (Cope, 1875) hook & Baird, 1986 [Colosteus newberryi Cope, 1875]
   |  |  `?- †S. sp. [Hook & Baird, 1992]
   |  `-- †Zatrachys senatus Cope, 1878 [Aspidosaurus serratus (Cope, 1881) Watson, 1919] [Acanthostoma, ?Acanthostomatops]
   `--+-- †Parioxys ferricolus [Parioxyidae]
      `--o †Eryopidae
         |-- †Chelyderpeton latirostris
         |--o †Clamorosaurus Gubin, 1983
         |  |-- †C. nocturnus Gubin, 1983
         |  `-- †C. borealis Gubin, 1983
         |--o †Eryops
         |  `-- †E. megacephalus
         |--o †Onchiodon Geinitz, 1861 [taxonomic history]
         |  |-- †O. labyrinthicus Geinitz, 1861 [taxonomic history]
         |  |?- †O.? foverolatum (Fritsch, 1901) Romer, 1947 [taxonomic history]
         |  |-- †O. manebachensis (Langehan, 1909)
         |  |-- †O. langenhani Werneburg, 1989
         |  `-- †O. sp.
         `-- †Osteophorus romeri Meyer, 1856 [Sclerocephalus romeri (Meyer, 1860) Fritsch, 1901

Reference(s):