( ( ( Several pieces ) ( of evidence ) ) ( ( are ( needed ( to ( show ( that ( ( a rock ) ( was ( ( used ( by ( a ( fossil animal ) ) ) ) ( to ( aid ( its digestion ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Several) (NNS pieces)) (PP (IN of) (NP (NN evidence)))) (VP (VBP are) (VP (VBN needed) (S (VP (TO to) (VP (VB show) (SBAR (IN that) (S (NP (DT a) (NN rock)) (VP (VBD was) (VP (VBN used) (PP (IN by) (NP (DT a) (JJ fossil) (NN animal))) (S (VP (TO to) (VP (VB aid) (NP (PRP$ its) (NN digestion)))))))))))))) (. .)))
Several pieces of evidence are needed to show that a rock was used by a fossil animal to aid its digestion.
(ROOT (S (NP (NP (DT The) (NN presence)) (PP (IN of) (NP (NP (DT an) (NN animal) (NN fossil)) (PP (IN in) (NP (DT a) (NN rock)))))) (VP (VBZ gives) (NP (NP (NN evidence)) (PP (IN of) (NP (DT the) (NN time) (NN period)))) (NP (NP (DT the) (NN animal)) (VP (VBN lived) (PP (IN in))))) (. .)))
The presence of an animal fossil in a rock gives evidence of the time period the animal lived in.