( ( a three ) ( - ( or ( ( four-chambered heart ) ; ) ) ) )
(ROOT (NP (NP (DT a) (CD three)) (PRN (: -) (CC or) (NP (JJ four-chambered) (NN heart)) (: ;))))
a three- or four-chambered heart;
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS chambers)) (PP (IN in) (NP (DT an) (NN amphibian) (NN heart))))) (. .)))