( ( ( The ( Dresbachian ( extinction event ) ) ) ( during ( the ( Late Cambrian ) ) ) ) ( ( ( was ( ( the second ) ( of ( two ( severe extinctions ) ) ) ) ) ( during ( ( the ( first period ) ) ( of ( the ( Paleozoic era ) ) ) ) ) ) ; ) )
(ROOT (S (NP (NP (DT The) (NNP Dresbachian) (NN extinction) (NN event)) (PP (IN during) (NP (DT the) (NNP Late) (NNP Cambrian)))) (VP (VBD was) (NP (NP (DT the) (NN second)) (PP (IN of) (NP (CD two) (JJ severe) (NNS extinctions)))) (PP (IN during) (NP (NP (DT the) (JJ first) (NN period)) (PP (IN of) (NP (DT the) (JJ Paleozoic) (NN era)))))) (: ;)))
The Dresbachian extinction event during the Late Cambrian was the second of two severe extinctions during the first period of the Paleozoic 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)))) (. .)))