( ( ( ( ( ( ( Sixty-five million ) years ) ( have ( passed ( since ( they ( became extinct ) ) ) ) ) ) , ) yet ) ( that ( is ( ( a ( brief time ) ) ( compared ( to ( ( their ( long reign ) ) ( upon ( the earth ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (QP (CD Sixty-five) (CD million)) (NNS years)) (VP (VBP have) (VP (VBN passed) (SBAR (IN since) (S (NP (PRP they)) (VP (VBD became) (ADJP (JJ extinct)))))))) (, ,) (CC yet) (S (NP (DT that)) (VP (VBZ is) (NP (NP (DT a) (JJ brief) (NN time)) (PP (VBN compared) (PP (TO to) (NP (NP (PRP$ their) (JJ long) (NN reign)) (PP (IN upon) (NP (DT the) (NN earth))))))))) (. .)))
Sixty-five million years have passed since they became extinct, yet that is a brief time compared to their long reign upon the earth.
(ROOT (S (NP (EX There)) (VP (VBP have) (VP (VBN been) (NP (CD five) (JJ major) (JJ massive) (NNS extinctions)) (SBAR (IN since) (S (NP (NN life)) (VP (VBD began) (PP (IN on) (NP (NN earth)))))))) (. .)))