( ( Having ( three chambers ) ) ( , ( ( the ( amphibian heart ) ) ( ( is ( rather ( unusual ( in ( that ( it ( has ( ( ( ( two atria ) and ) only ) ( a ( single ventricle ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (S (VP (VBG Having) (NP (CD three) (NNS chambers)))) (, ,) (NP (DT the) (NN amphibian) (NN heart)) (VP (VBZ is) (ADJP (RB rather) (JJ unusual) (PP (IN in) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ has) (NP (NP (CD two) (NN atria)) (CC and) (RB only) (NP (DT a) (JJ single) (NN ventricle))))))))) (. .)))
Having three chambers, the amphibian heart is rather unusual in that it has two atria and only a single ventricle.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS chambers)) (PP (IN in) (NP (DT an) (NN amphibian) (NN heart))))) (. .)))