Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The end is set at a major extinction event called Grande Coupure, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay, resulting in the devastation of non ornithopoid Poposaurids and the vast majority of the Prestosuchids and As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.