In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between ~56 Ma and ~49 Ma (million years ago).
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In the geologic timescale the Ypresian ən is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between {ma|Ypresian|and} {Ma|Lutetian|Ma}, is preceded by the Thanetian age (part of the Paleocene) and is followed by the Eocene Lutetian age. The Ypresian is sometimes included with the Lutetian in an Early Eocene subepoch...
Found on
http://en.wikipedia.org/wiki/Ypresian
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