Final answer:
During the Eocene Epoch, two notable primate groups evolved. The prosimians, ancestors to modern lemurs and related species, and early simians, which led to New World monkeys such as marmosets and howler monkeys.
Step-by-step explanation:
Primate Evolution in the Eocene Epoch
The Eocene Epoch, a significant period in primate evolution, began around 54 million years ago (MYA) and ended about 34 MYA. It witnessed the emergence of early primates that were the ancestors of today’s strepsirrhines and haplorhines. Two primate groups that evolved from the Eocene are specifically influential: prosimians and the early simians.
Prosimians, including lemurs, aye-ayes, lorises, and tarsiers, possess distinctive features such as a toothcomb and/or a grooming claw, which are found in present-day strepsirrhine primates. These Eocene prosimians were the ancestors to modern prosimians and contributed to the current diversity within the strepsirrhine group.
The simians that emerged during the Eocene led to the later development of monkeys and apes. Ceboids, or New World monkeys of South America, evolved from these early simians and are characterized by tails that allow them to grasp and hang from tree branches. This group includes marmosets and howler monkeys. Another crucial evolutionary step during the Eocene was the development of the postorbital bar, allowing for more advanced eye structure and contributing significantly to primate evolutionary success.