- In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between 56 and 47.8 Ma, is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian is consistent with the lower Eocene.
- Lutetian (Wikipedia)
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between 47.8 and 41.2 Ma. The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene Subepoch.
- Eocene (Wikipedia)
The Eocene (IPA: /ˈiːəsiːn, ˈiːoʊ-/ EE-ə-seen, EE-oh-) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name Eocene comes from the Ancient Greek ἠώς (ēṓs, “dawn”) and καινός (kainós, “new”) and refers to the “dawn” of modern (’new’) fauna that appeared during the epoch.