( probable ( ( tetrapod ancestor ) . ) )
(ROOT (S (NP (JJ probable)) (VP (VBD tetrapod) (NP (NN ancestor))) (. .)))
probable tetrapod ancestor.
(ROOT (S (NP (NNS Caecillians)) (VP (VBD evolved) (PP (IN from) (NP (JJ tetrapod) (NNS ancestors)))) (. .)))