What type of primates radiated during the late Oligocene period?

During the late Oligocene period, the primate group that truly flourished and diversified was the New World monkeys. This time frame, which dates from approximately 33.9 to 23 million years ago, marks a significant phase in primate evolution where distinct evolutionary lineages began to form in different regions.

New World monkeys, or Platyrrhines, evolved in South America and developed unique adaptations that set them apart from their Old World counterparts. Features such as their prehensile tails, broad noses, and different social behaviors can be traced back to this period. The subsequent fossil evidence supports the idea that many species started to emerge and diversify at this time.

In contrast, other groups like Old World monkeys, apes, and euprimates did not see a similar level of radiation during this period. Old World monkeys were primarily associated with the later Miocene, while apes, which represent a different lineage of primates, evolved later as well. Euprimates, referring to the more modern-looking primates that emerged earlier in the Eocene, were also not the focus of diversification during the late Oligocene.