"[Pisces]"
   Class Cephalaspidomorphi Kiaer & Stensiö, 1920 see Class Osteostraci Lankester, 1868
     Order Petromyzontiformes Berg, 1940 - lampreys
       Family Petromyzontidae Bonaparte, 1831 - lampreys
         1 Subfamily Petromyzontinae
         2 Subfamily Geotriinae see Family Geotriidae Gill, 1893
         3 Subfamily Mordaciinae see Family Mordaciidae Gill, 1893