(S (S (BASENP (PRP It)) (VP (VBD was) (VP (VP (VBN kept) (PP (IN in) (BASENP (JJ excellent) (NN condition)))) (PP (IN by) (NP (NP (BASENP (DT a) (JJ thick) (NN layer)) (PP (IN of) (BASENP (NN sheep) (NN excrement)))) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VP (VBD acted) (PP (IN as) (BASENP (DT a) (NN seal)))) (COMMA ,) (S (VP (VBG helping) (S (BASENP (PRP it)) (VP (VB survive) (BASENP (DT the) (NN millennia)))))))))))))) (PERIOD .))