( ( have ( skeletons ( of ( ( ( cartilage , ) not ) bone ) ) ) ) . )
(ROOT (S (VP (VB have) (NP (NP (NNS skeletons)) (PP (IN of) (NP (NP (NN cartilage)) (, ,) (RB not) (NP (NN bone)))))) (. .)))
have skeletons of cartilage, not   bone.
(ROOT (S (ADVP (RB Early) (PP (IN in) (NP (NP (DT the) (NN development)) (PP (IN of) (NP (DT a) (JJ human) (NN fetus)))))) (, ,) (NP (DT the) (NN skeleton)) (VP (VBZ is) (VP (VBN made) (ADVP (RB entirely)) (PP (IN of) (NP (NN cartilage))))) (. .)))