( ( In ( ( the absence ) ( of endoskeletons ) ) ) ( , ( exoskeletons ( ( ( are often ) ( ( ( highly devel ) - ) ( oped ( among ( the invertebrates ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (DT the) (NN absence)) (PP (IN of) (NP (NNS endoskeletons))))) (, ,) (NP (NNS exoskeletons)) (VP (VBP are) (ADVP (RB often)) (ADJP (ADJP (RB highly) (JJ devel)) (: -) (ADJP (JJ oped) (PP (IN among) (NP (DT the) (NNS invertebrates)))))) (. .)))
In the absence of endoskeletons, exoskeletons are often highly devel-  oped among the invertebrates.
(ROOT (S (NP (NNS Humans)) (VP (VBP possess) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN endoskeleton))) (. .)))