Class Mammalia Linnaeus, 1758 - mammals
   Subclass †Allotheria Marsh, 1880
     Order †Multituberculata Cope, 1884
       Suborder †"Plagiaulacida" Ameghino, 1889 [paraphyletic]
         †Plagiaulacid line
           Family †Plagiaulacidae Gill, 1872
             Genus †Plagiaulaxᵀ Falconer, 1857 [monotypic]
               1 †Plagiaulax becklesii Falconer, 1857