( Mammals ( , ( ( like birds ) ( , ( ( possess ( a ( four-chambered heart ) ) ) . ) ) ) ) )
(ROOT (S (NP (NNS Mammals)) (, ,) (PP (IN like) (NP (NNS birds))) (, ,) (VP (VBP possess) (NP (DT a) (JJ four-chambered) (NN heart))) (. .)))
Mammals, like birds, possess a four-chambered heart .
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD four) (NNS chambers)) (PP (IN in) (NP (DT the) (NN heart))))) (. .)))