( It ( ( ( is possible ) ( that ( ( ( the reptiles ) ( that ( were ( ( the ancestors ) ( of birds ) ) ) ) ) ( also ( had wings ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (ADJP (JJ possible)) (SBAR (IN that) (S (NP (NP (DT the) (NNS reptiles)) (SBAR (WHNP (WDT that)) (S (VP (VBD were) (NP (NP (DT the) (NNS ancestors)) (PP (IN of) (NP (NNS birds)))))))) (ADVP (RB also)) (VP (VBD had) (NP (NNS wings)))))) (. .)))
It is possible that the reptiles that were the ancestors of birds also had wings.
(ROOT (S (NP (NP (DT The) (NN bird) (NN ancestor)) (SBAR (WHNP (WDT that)) (S (VP (VBD lived) (PP (IN in) (NP (NNS trees))))))) (VP (VBD developed) (NP (NP (NNS wings)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADVP (RB commonly)) (VP (VBN associated) (PP (IN with) (NP (NNS birds))))))))) (. .)))
The bird ancestor that lived in trees developed wings, which is commonly associated with birds.