但是很不幸的是，这段迅速的进化过程发生于中白垩纪的一千五百万年间，而这段时期的鲜有化石记录。
"But there were a hundred million years of evolution to play with."
海洋沉积物中浮游生物的这种变化标志着白垩纪和第三纪的分界线。
This change in plankton found in marine deposits is what marks the boundary between the Cretaceous and the Tertiary.
来自不同来源的数据，包括存留在海底沉积物中的地球化学依据，表明晚白垩纪的气候比如今的要温和。
Data from diverse sources, including geochemical evidence preserved in seafloor sediments, indicate that the Late Cretaceous climate was milder than today's.
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