( This ( ( is ( ( the beginning ) ( of ( ( their ( first encounter ) ) ( in ( the ( Cambrian era ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NP (DT the) (NN beginning)) (PP (IN of) (NP (NP (PRP$ their) (JJ first) (NN encounter)) (PP (IN in) (NP (DT the) (NNP Cambrian) (NN era))))))) (. .)))
This is the beginning of their first encounter in the Cambrian era.
(ROOT (S (NP (NP (DT The) (JJ first) (NN period)) (PP (IN of) (NP (DT the) (JJ paleozoic) (NN era)))) (VP (VBD was) (VP (VBN called) (NP (NN cambrian)))) (. .)))