After Benson, 2012

<==o Synapsida Osborn, 1903 (yksiohimoaukkoiset amniootit; mammal-like amniotes)
   |--+-- †Ophiacodontidae Nopcsa, 1923
   |  `-- †Varanopseidae (Romer & Price, 1940) Langston & Reisz, 1981 [Varanopsidae (Romer & Price, 1940); Varanopidae (Romer & Price, 1940) Reisz & Dilkes, 2003; Benson, 2012]
   `--+--o †Caseasauria Williston, 1912 sensu Reisz, 1986?
      |  |--o †Eothyrididae Romer & Price, 1940
      |  |  |-- †Eothyris parkeyi Romer, 1937
      |  |  `-- †Oedaleops campi Langston, 1962
      |  `-- †Caseidae Williston, 1912
      `--o Eupelycosauria Kemp, 1982 (purjeliskot; nisäkäslikot ja nisäkkäät; fin-backed sphenacodonts, therapsids and mammals)
         |-- †Edaphosauridae Cope, 1882 sensu Modesto, 1995
         `--o Sphenacodontia Williston 1912 (non Marsh, 1878) sensu Romer & Price, 1940 [Sphenacodontidae Marsh, 1878 sensu lato]
            |?- †Bathygnathus borealis [AMNH-2325]
            |?- †Macromerion Fritsch, 1879 [Macrornerion (an OCR error)]
            |?- †Milosaurus mccordi DeMar, 1970
            |?- †Tetraceratops insignis Matthew, 1908
            |?- †Palaeohatteria longicaudata Credner, 1888 [Haplodus, paraphyletic Haplodontinae]
            |--o †Haptodus Gaudry, 1886 sensu Currie, 1977 [paraphyletic Haplodontinae]
            |  |-- †H. beylei Gaudry. 1886
            |  |-- †H. grandis Paton, 1974
            |  `-- †H. garnettensis Currie, 1977
            `--+-- †Pantelosaurus saxonicus Von Huene, 1925 [Haplodus, paraphyletic Haplodontinae]
               `--o Sphenacodontoidea Williston 1912 (non Marsh, 1878)
                  |-- Therapsida Broom, 1905 (nisäkäsmäiset synapsidit, mammallike synapsids)
                  `--o Sphenacodontidae Marsh, 1878 sensu Benson, 2012
                     |-- †Cutleria wilmarthi Lewis & Vaughn, 1965 [Haplodus, paraphyletic Haplodontinae]
                     `-- †Sphenacodontidae Marsh, 1878 (non Williston 1912) sensu stricto

Synapsida incertae sedis:

Echinerpeton intermedium Reisz, 1972
    †Elcabrosaurus baldwiniNitosaurus jacksonorum Romer, 1937 [AMNH-4796]
    †Poecilospondylus francisiScoliomus puercensis Williston & Care, 1913
    †Trichasaurus texensis Williston, 1913
    †Wangwosaurus tayuensis Young, 1979
    †Xyrospondylus Rice et al., 1982

    †Nikkasauridae Ivakhnenko, 2000
        †Nikkasaurus tatarinovi Ivakhnenko, 2000
        †Reiszia Ivakhnenko, 2000
            †R. gubini Ivakhnenko, 2000 (Type)
            †R. tippula Ivakhnenko, 2000

After Romer & Price, 1940 (from Benson, 2012)

<==o Synapsida
   |-- †Eothyrididae [paraphyletic Ophiacodontia]
   `--+-- †Ophiacodontidae [paraphyletic Ophiacodontia]
      `--+--+-- †Edaphosauridae
         |  `-- †Caseidae
         `--+-- †Varanopseidae
            `--+-- †Sphenacodontidae
               `-- Therapsida

After Reisz, 1980 (from Benson, 2012)

<==o Synapsida
   |--o †Caseasauria
   |  |-- †Eothyrididae
   |  `-- †Caseidae
   `--+-- †Edaphosauridae
      `--+-- †Ophiacodontidae
         `--+-- †Varanopseidae
            `--+-- †Sphenacodontidae
               `-- Therapsida

After Brinkman & Eberth, 1983 (from Benson, 2012)

<==o Synapsida
   |--+-- †Varanopseidae
   |  `--o †Caseasauria
   |     |-- †Eothyrididae
   |     `-- †Caseidae
   `--+-- †Ophiacodontidae
      `--+-- †Edaphosauridae
         `--+-- †Sphenacodontidae
            `-- Therapsida

After Reisz, 1986 (from Benson, 2012)

<==o Synapsida
   |--o †Caseasauria
   |  |-- †Eothyrididae
   |  `-- †Caseidae
   `--+-- †Varanopseidae
      `--+-- †Ophiacodontidae
         `--+-- †Edaphosauridae
            `--+-- †Sphenacodontidae
               `-- Therapsida

After Laurin & Reisz, 1997 [“The Tree of Life”]

<==o Synapsida
   |--o †Caseasauria
   |  |-- †Eothyrididae
   |  `-- †Caseidae
   `--o Eupelycosauria
      |-- †Varanopseidae
      `--+-- †Ophiacodontidae
         `--+-- †Edaphosauridae
            `--o Sphenacodontia [Sphenacodontidae sensu lato]
               |-- †Haptodus
               `--+-- †Palaeohatteria
                  `--+-- †Pantelosaurus
                     `--+-- †Cutleria
                        `--o Sphenacodontoidea
                           |-- †Sphenacodontidae
                           `-- Therapsida

Reference(s):

 

Special thanks to:

Jos H. M. Dols, for gathering additional information and species.