60 million years ago: earliest primate fossil.
The remains of the earliest primate date back to 60 million years ago and were found in Adrar Mgom, Morocco. Another more recent primate specimen is Plesiadapis. It is very similar to a tarsier and lived in North America and Europe 58-55 million years ago.
Since fossilization of a specimen is a very rare event, logical reasoning leads us to the conclusion that primates must have existed long before these dates. This means they should have been contemporaries of the dinosaurs for millions of years. The scientific consensus is that primates arose between 77 and 85 million years ago. There are at present around 200 species and scientists estimate there must have been in the past more than 6,500 different species.
Primates key features are hands and feet with five fingers and toes, all of them with keratin nails, an opposable thumb on hands and feet, two mammary glands and stereoscopic color vision. Primates are an order of mammals that includes prosimians, tarsiers, New World monkeys, Old World monkeys and apes.
The New World monkeys, called platyrrhines, are characterized by long, prehensile tails, flattened snouts, and nostrils pointing laterally. By contrast, the Old World monkeys or catarrhines, do not have prehensile tails and their nostrils are round and pointing downward.
Old World monkeys gave rise to apes 33-24 million years ago. The main feature of the latter is they never have a tail. African apes are gorillas, chimpanzees, bonobos, and humans. Asian apes are gibbons and orangutans.
It is interesting to know that the word primate was first used by Carl Linnaeus, referring to the first in a theological sense. This meaning is ignored at present.