However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display a character unique to a sub-set of the crown group.
Hăk ǝd ǝjja awen, tǝmtar n as axfuri n tăqqǝmt tan takabut n filum assohăt fal as ǝlzăm ad ǝsăkin sămăl ǝyyăn ǝ tăqqǝmt tan takabut