( ( A petrifaction ) ( ( ( ( is ( three dimensional ) ) but ) ( shows ( only ( external features ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN petrifaction)) (VP (VP (VBZ is) (NP (CD three) (NN dimensional))) (CC but) (VP (VBZ shows) (NP (RB only) (JJ external) (NNS features)))) (. .)))
A petrifaction is three dimensional but shows only external features.
(ROOT (S (NP (NNP Contour) (NNS lines)) (VP (VBP show) (NP (NP (DT the) (JJ three-dimensional) (NN shape)) (PP (IN of) (NP (NN land))))) (. .)))