Sakéwanten nyihnayang fosil punika ngranjing ring kelompok mahkota filum wantah sukil pisan, santukan mangda prasida nyihnayang karakter sané unik ring sub-set saking kelompok mahkota punika.
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.