After Carroll, 1967, Laurin & Reisz, 1997, Lee & Spencer, 1997, and Kissel, 2010

<==o †Diadectomorpha Watson, 1917
   |--o †Limnoscelidae Williston, 1911
   |  |--o †Limnoscelis Williston, 1911; L.Perm. SWNAm.
   |  |  |-- †L. paludis Williston, 1911
   |  |  `-- †L. dynatis Berman & Sumida, 1990
   |  |--o †Limnosceloides Romer, 1952; L.Perm. SWNAm.
   |  |  |-- L. dunkardensis Romer, 1952
   |  |  `-- L. brachycoles Langston, 1966
   |  |-- †Limnoscelops longifemur Levis & Vaughn, 1965; L.Perm. SWNAm.
   |  |-- †Limnostygis relictus Carroll, 1967, L.Carb. NENAm.
   |  `?- †Romeriscus periallus Baird & Carroll, 1967 [nomen dubium sensu Laurin & Reisz, 1992]
   `--+?- †Tseajaia campi Vaughn, 1964 [Tseajaiidae]
      `--o †Diadectidae
         |?- †Phanerosaurus naumanni Meyer 1860
         |?- †Stephanospondylus pugnax (Geinitz & Deichmueller, 1882) Stappenbeck, 1905 [Phanerosaurus pugnax Geinitz & Deichmueller, 1882]
         |-- †Ambedus pusillus Kissel & Reisz, 2004
         `--+-- †Oradectes sanmiguelensis (Lewis & Vaughn, 1965) Kissel, 2010 [Diadectes sanmiguelensis Lewis & Vaughn, 1965] [Validity of Oradectes qustionable due publication in Thesis]
            `--+-- †Orobates pabsti Berman, Henrici, Kissel, Sumida, & Martens, 2004 [Diadectidae genera et species indet. (Berman & Henrici, 2003)] L.Perm. CEu.
               `--+?- †Alveusdectes fenestratus Liu & Bever, 2015
                  |--o †Desmatodon Case, 1908
                  |  |-- †D. hollandi Case, 1908
                  |  `-- †D. hesperis Vaughn, 1969 [Sepeliodon hesperis (Vaughn, 1969)]
                  `--+-- †Silvadectes absitus (Berman et al., 1998) Kissel, 2010 [Diadectes absitus Berman et al., 1998] [Validity of Silvadectes qustionable due publication in Thesis (Kissel, 2010)]
                     `==o †Diadectes Cope, 1878 [Nothodon Marsh, 1878; Empedocles Cope, 1878; Helodectes Cope, 1880; Empedias Cope, 1883; Chilonyx Cope, 1883; Bolbodon Cope, 1896; Diadectoides Case, 1911; Animasaurus Case & Williston, 1912]
                        |?- †Diadectes carinatus (Case & Williston, 1912) [Animasaurus carinatus Case & Williston, 1912]
                        |?- †Diadectes lentus (Marsh, 1878) [Nothodon lentus Marsh, 1878]
                        |-- †Diadectes tenuitectus (Cope, 1896) [Bolbodon tenuitectes Cope 1896; Diadectes maximus Case 1910; Diadectoides cretin Case 1911; Diadectes huenei Broom 1914]
                        `--+-- †Diadectes sideropelicus Cope, 1878 [type] [Diadectes latibuccatus Cope 1878a; Empecocles latibuccatus (Cope 1878a); Empedias latibuccatus (Cope 1878a); Bolosaurus rapidens Cope 1878a; Chilonyx rapidens (Cope 1878a); Empedocles alatus Cope 1878a; Empedias alatus (Cope 1878a); Diadectes molaris Cope 1878b; Empedocles molaris (Cope 1878b); Empedias molaris (Cope 1878b); Diadectes phaseolinus Cope 1880b; Empedias phaseolinus (Cope 1880b); Helodectes paridens Cope 1880b; Helodectes isaaci Cope 1880b; Empedias fissus Cope 1883; Diadectes biculminatus Cope 1896.]
                           `-- †Diasparactus zenos Case, 1910 [Diadectes zenos (Case, 1910) Kissel, 2010]

After Liu & Bever, 2015

<==o †Diadectomorpha
   |-- †Limnoscelis
   `--+-- †Tseajaia
      `--+-- †Ambedus
         `--+-- †Oradectes
            `--+-- †Alveusdectes
               |-- †Desmatodon
               `--+-- †Diadectes
                  `-- †Diasparactus

Reference(s):

  • Liu, J. & Bever, G. S., 2015: The last diadectomorph sheds light on Late Palaeozoic tetrapod biogeography.
    –Biology Letters: Vol. 11, #5, in press [doi: 10.1098/rsbl.2015.0100]

After Kissel, 2010

<==o †Diadectomorpha
   |-- †Limnoscelis
   `--+-- †Tseajaia
      `--o †Diadectidae
         |-- †Ambedus
         `--+-- †Oradectes
            `--+-- †Desmatodon [Sepeliodon]
               `--+-- †Diadectes tenuitectus
                  `--+--  †Diadectes sideropelicus
                     `-- †Diasparactus

Reference(s):

  • Kissel, R. A., 2010: Morphology, phylogeny, and evolution of Diadectidae (Cotylosauria: Diadectomorpha). –PhD dissertation, University of Toronto, Canada,
    [url:http://hdl.handle.net/1807/24357]

Reference(s):