( ( ( ( ( Those ( are ( ( the ( only characteristics ) ) ( required ( of ( all mammals ) ) ) ) ) ) , ) but ) ( ( most mammals ) ( bear ( ( ( ( ( ( ( ( live young ) , ) ( ( ( maintain ( a ( constant ( body temperature ) ) ) ) ( despite ( changing ( climatic conditions ) ) ) ) ( -LRB- ( warm-blooded -RRB- ) ) ) ) , ) ( have ( differentiated teeth ) ) ) , ) and ) ( have ( ( four limbs ) ( -LRB- ( ( ( ( ( ( ( two ( legs ( and ( two arms ) ) ) ) , ) ( four legs ) ) , ) or ) ( ( a pair ) ( of ( ( flippers and ) fins ) ) ) ) -RRB- ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT Those)) (VP (VBP are) (NP (NP (DT the) (JJ only) (NNS characteristics)) (VP (VBN required) (PP (IN of) (NP (DT all) (NNS mammals))))))) (, ,) (CC but) (S (NP (JJS most) (NNS mammals)) (VP (VBP bear) (VP (VP (VB live) (ADJP (JJ young))) (, ,) (VP (VB maintain) (NP (DT a) (JJ constant) (NN body) (NN temperature)) (PP (IN despite) (S (VP (VBG changing) (NP (JJ climatic) (NNS conditions))))) (PRN (-LRB- -LRB-) (ADJP (JJ warm-blooded)) (-RRB- -RRB-))) (, ,) (VP (VB have) (VP (VBN differentiated) (NP (NNS teeth)))) (, ,) (CC and) (VP (VB have) (NP (NP (CD four) (NNS limbs)) (PRN (-LRB- -LRB-) (NP (NP (CD two) (NNS legs) (CC and) (CD two) (NNS arms)) (, ,) (NP (CD four) (NNS legs)) (, ,) (CC or) (NP (NP (DT a) (NN pair)) (PP (IN of) (NP (NNS flippers) (CC and) (NNS fins))))) (-RRB- -RRB-))))))) (. .)))
Those are the only characteristics required of all mammals, but most mammals bear live young, maintain a constant body temperature despite changing climatic conditions (warm-blooded), have differentiated teeth, and have four limbs (two legs and two arms, four legs, or a pair of flippers and fins).
(ROOT (S (NP (DT All) (NNS mammals)) (VP (VBP have) (NP (CD four) (NNS limbs))) (. .)))