( ( a ( common ancestry ) ) ( is ( ( the ( primary criteria ) ) ( used ( to ( classify ( organisms ( -LRB- ( ( finding clades ) -RRB- ) ) ) ) ) ) ) ) )
(ROOT (S (NP (DT a) (JJ common) (NN ancestry)) (VP (VBZ is) (NP (NP (DT the) (JJ primary) (NNS criteria)) (VP (VBN used) (S (VP (TO to) (VP (VB classify) (NP (NP (NNS organisms)) (PRN (-LRB- -LRB-) (NP (NN finding) (NNS clades)) (-RRB- -RRB-)))))))))))
a common ancestry is the primary criteria used to classify organisms (finding clades)
(ROOT (S (NP (DT A) (NN clade)) (VP (VBZ is) (NP (NP (CD one) (NN way)) (PP (IN of) (NP (VBG classifying) (NNS organisms))))) (. .)))