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 †Spalacotheridium Cifelli, 1990 †Spalacotheridium noblei Cifelli & Madsen, 1999