( Reptiles ( ( are ( tetrapod ( ( vertebrates , ) ( creatures ( that ( either ( have ( ( ( ( ( ( four limbs ) or ) , ) ( like snakes ) ) , ) ( being ( descended ( from ( four-limbed ancestors ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Reptiles)) (VP (VBP are) (VP (VBN tetrapod) (NP (NP (NNS vertebrates)) (, ,) (NP (NP (NNS creatures)) (SBAR (WHNP (WDT that)) (S (ADVP (RB either)) (VP (VBP have) (NP (NP (CD four) (NNS limbs)) (CC or) (, ,) (PP (IN like) (NP (NNS snakes))) (, ,) (VP (VBG being) (VP (VBD descended) (PP (IN from) (NP (JJ four-limbed) (NNS ancestors))))))))))))) (. .)))
Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, being descended from four-limbed ancestors.
(ROOT (S (NP (NNP Birds)) (VP (VBP have) (NP (CD four) (NNS limbs))) (. .)))