Subclass †Heterostraci Lankester, 1868
   Family †Cyathaspididae Kiaer, 1932, nom. praeval.
     Subfamily †Irregulareaspidinae Denison, 1964
       1 Genus †Irregulareaspis Zych, 1931
       2.1 Genus †Dinaspidella Strand, 1934
       2.2 Genus †Nahanniaspis Dineley & Loeffler, 1976