Class Mammalia Linnaeus, 1758 - mammals
   †"Symmetrodontans" Simpson, 1925, incertae sedis see Infraclass Symmetrodonta Simpson, 1925
     Superlegion Trechnotheria McKenna, 1975 see Clade Trechnotheria McKenna 1975
       Family †Spalacotheriidae Marsh, 1887
         Subfamily †Spalacolestinae Cifelli & Madsen, 1999
           Genus †Symmetrodontoides Fox, 1976
             1 †Symmetrodontoides canadensisᵀ Fox, 1976
             2 †Symmetrodontoides foxi Cifelli & Madsen, 1986
             3 †Symmetrodontoides oligodontos Cifelli, 1990