( ( ( Amphibians and ) ( ( most living ) reptiles ) ) ( ( have ( ( ( a ( three-chambered heart ) ) , ) ( which ( ( has usually ) ( been ( ( regarded ( as inferior ) ) ( to ( ( the ( four-chambered heart ) ) ( of ( living ( ( mammals and ) birds ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Amphibians)) (CC and) (NP (ADJP (RBS most) (JJ living)) (NNS reptiles))) (VP (VBP have) (NP (NP (DT a) (JJ three-chambered) (NN heart)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ has) (ADVP (RB usually)) (VP (VBN been) (VP (VBN regarded) (ADJP (RB as) (JJ inferior)) (PP (TO to) (NP (NP (DT the) (JJ four-chambered) (NN heart)) (PP (IN of) (NP (NN living) (NNS mammals) (CC and) (NNS birds)))))))))))) (. .)))
Amphibians and most living reptiles have a three-chambered heart, which has usually been regarded as inferior to the four-chambered heart of living mammals and birds.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS chambers)) (PP (IN in) (NP (DT a) (JJ reptiles) (NN heart))))) (. .)))