( They ( ( produce ( ( amniotic eggs ) ( that ( have ( a ( ( very heavy ) ( calcium ( carbonate shell ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP produce) (NP (NP (JJ amniotic) (NNS eggs)) (SBAR (WHNP (WDT that)) (S (VP (VBP have) (NP (DT a) (ADJP (RB very) (JJ heavy)) (NN calcium) (NN carbonate) (NN shell))))))) (. .)))
They produce amniotic eggs that have a very heavy calcium carbonate shell.
(ROOT (S (NP (NNS Mammals)) (VP (VP (VBP have) (NP (CD four) (NNS limbs))) (CC and) (VP (VBP produce) (NP (JJ amniotic) (NNS eggs)))) (. .)))