( It ( ( is ( ( ( drawn ( by horses ) ) , ) ( ( more commonly ) ( by ( ( birds or ) ( winged steeds ) ) ) ) ) ) ; ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (VP (VBN drawn) (PP (IN by) (NP (NNS horses))) (, ,) (ADVP (ADVP (RBR more) (RB commonly)) (PP (IN by) (NP (NP (NNS birds)) (CC or) (NP (JJ winged) (NNS steeds))))))) (: ;)))
It is drawn by horses, more commonly by birds or winged steeds;
(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.