( 1998 ) The top of the Asselian stage ( the base of the Sakmarian stage ) is at the first appearance of the species " Streptognathodus postfusus " .
Head entity: sakmarian Q912962 14
Tail entity: asselian Q740340 7
Relation (head \u2192 tail): P156
Inverse relation (tail \u2192 head): P155