( ( ( In ( the mid-1980s ) ) ( researchers found ) ) ( ( fossil animal ) ( ( burrows ( in ( rocks ( of ( the ( Ordovician Period ) ) ) ) ) ) ; ) ) )
(ROOT (S (SBAR (S (PP (IN In) (NP (DT the) (NNS mid-1980s))) (NP (NNS researchers)) (VP (VBD found)))) (NP (JJ fossil) (NN animal)) (VP (VBZ burrows) (PP (IN in) (NP (NP (NNS rocks)) (PP (IN of) (NP (DT the) (NNP Ordovician) (NN Period)))))) (: ;)))
In the mid-1980s researchers found fossil animal burrows in rocks of the Ordovician Period;
(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.