( ( ( The ( earliest period ) ) ( of ( the ( Palaeozoic era ) ) ) ) ( ( is ( called ( the ( Cambrian Period ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJS earliest) (NN period)) (PP (IN of) (NP (DT the) (JJ Palaeozoic) (NN era)))) (VP (VBZ is) (VP (VBN called) (NP (DT the) (NNP Cambrian) (NN Period)))) (. .)))
The earliest period of the Palaeozoic era is called the Cambrian Period.
(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)))) (. .)))