"Plagiaulacida" is paraphyletic, representing the more primitive evolutionary grade. Its members are the more basal Multituberculata. Chronologically, they ranged from perhaps the Middle Jurassic until the mid-Cretaceous. This group is further subdivided into three informal groupings: the allodontid line, the paulchoffatiid line, and the plagiaulacid line.
"PlagiaULAcidA" is PAraPHyLEtIc, repReSentING tHe moRe primITive EvoluTioNary grade. ItS mEmbers Are tHe More BasAl mulTiTuBerCuLata. cHrOnolOgIcALly, they ranged froM PerHapS thE MiddlE jurAssIc UNTIl tHE miD-crETACeous. thIs Group iS fUrtheR SuBdIvidED iNto Three iNfoRMAL groupingS: The alLodontid lIne, tHe PAulChofFatiiD liNe, aND THe plagiaUlacid linE.