Children (9 direct children, 166 direct and indirect children):
Lamprey
(tree size 124)
Petromyzontiformes
Procephalaspis
Tremataspidiformes
(tree size 10)
Cephalaspidiformes
(tree size 5)
Birkeniiformes
(tree size 7)
Cephalaspidida
Osteostraciformes
(tree size 6)
Pituriaspidiformes
Ateleaspidiformes
(tree size 5)