( ( ( The layers ) ( of ( thick skin ) ) ) . )
(ROOT (NP (NP (DT The) (NNS layers)) (PP (IN of) (NP (JJ thick) (NN skin))) (. .)))
The layers of thick skin .
(ROOT (S (NP (NP (DT The) (JJ thick) (NN skin)) (, ,) (VP (VBN found) (ADVP (RB only)) (PP (IN on) (NP (NP (NP (DT the) (NNS palms)) (PP (IN of) (NP (DT the) (NNS hands)))) (CC and) (NP (NP (DT the) (NNS soles)) (PP (IN of) (NP (DT the) (NNS feet))))))) (, ,)) (VP (VBZ has) (NP (DT an) (JJ extra) (NN layer))) (. .)))