Oligocene (Pt 11): Early Monkeys and Two-Ton Herbivores

Arsinoitherium

Because the Oligocene is so much further back in time than the later epochs, especially the Pliocene and Pleistocene, there are more gaps in our knowledge of it. That it's also much shorter than the epochs to either side of it means that those gaps can, proportionately speaking, occupy far more of its length. One of the places where such a gap is particularly noticeable is the history of primates.

Monkeys first appeared in Africa in the latter half of the preceding epoch, but their early record is patchy. This is likely because many of the earliest monkeys lived in areas that simply weren't conducive to forming fossils - although the fact that many parts of Africa have not had the same detailed paleontological surveys that other continents have may also be a factor. Much of the history of the primates during the epoch is a blank... but not entirely.