When did Primates first appear?

After an ‘interesting’ discussing last night I have tried to find the answer to the question ‘When did primates first appear?’ After reading wiki and a couple of other articles the following seems to encompass the latest perceived understanding. There is a bit here for all sides of the debate: – Deskarati

1million008

Many people take an understandably human-centered view of primate evolution, focusing on the bipedal, large-brained hominids that populated the jungles of Africa a few million years ago. But the fact is that primates as a whole–a category of megafauna mammals that includes not only humans and hominids, but monkeys, apes, lemurs, baboons and tarsiers–have a deep evolutionary history that stretches as far back as the age of dinosaurs.

purgatorius

purgatorius

The first mammal that palaeontologists have identified as possessing primate-like characteristics was Purgatorius, a tiny, mouse-sized creature of the late Cretaceous period (just before the K/T Impact Event that rendered the dinosaurs extinct). Although it looked more like a tree shrew than a monkey or ape, Purgatorius had a very primate-like set of teeth, and it (or a close relative) may have spawned the more familiar primates of the Cenozoic Era. (Genetic sequencing studies suggest that the earliest primate ancestor may have lived a whopping 20 million years before Purgatorius, but as yet there’s no fossil evidence for this mysterious beast.)

archicebus

archicebus

Recently, scientists have touted the equally mouse-like Archicebus, which lived 10 million years after Purgatorius, as the first true primate, and the anatomic evidence in support of this hypothesis is even stronger. What’s confusing about this is that the Asian Archicebus seems to have lived around the same time as the North American and Eurasian Plesiadapis, a much bigger, two-foot-long, tree-dwelling, lemur-like primate with a rodent-like head. The teeth of Plesiadapis displayed the early adaptations necessary for an omnivorous diet–a key trait that allowed its descendants tens of millions of years down the line to diversify away from trees and toward the open grasslands. Via Evolution – The Story of Prehistoric Primates.

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4 Responses to When did Primates first appear?

  1. Phil Krause says:

    I would just like to make things a little clearer. Our discussions were more specifically, did mammals appear before or after the KT extinction event 66 million years ago where 75% of all animal species died out including all the non-avian dinosaurs?
    Purgatorius was not a primate but a proto-primate or for-runner of primates. It was first found at Purgatory Hill (hence its name) in eastern Montana in deposits believed to be 63 million years old. This animal did not have any obvious features of primates such as hands, grasping feet or flat face with forward facing eyes. The only similarities were with its teeth which were omnivorous. It is thought to have given rise to both plesiadapiformes and primates.
    Plesiadapiformes is an extinct order of mammals which is either closely related to primates or a precursor of them. They first appear in the fossil record between 65 and 55 million years ago. It is thought that these were the first mammals to have developed finger nails in place of claws.
    Based on fossil evidence, the earliest known true primates were represented by the genus Teilhardina date to 55.8 million years old. This was a marmoset like primate that lived about 56-47 million years ago. Archicebus is a genus of primate also from around 55 million years ago. This is the oldest complete fossil primate skeleton discovered to date.
    To date there is no fossil evidence of mammals older than 55.8 million years ago. The only study, I have seen are molecular clock studies that suggest that the primate branch may be as old as 85 million years ago. These are notoriously inaccurate as they rely on genetic mutations happening on a consistently regular basis and they compare different primates and close relatives genes and extrapolate back to when they would have been the same before mutations made them different.

  2. Naan Glozi says:

    The picture of the Purgatorius looks very much closer to the rodent family than the primate family. Does that mean that us primates came from rats?

  3. Phil Krause says:

    The first multituberculate (rodent like) complete fossil skeleton of Rugosoden was found in China dating to 160 million years ago. It bears a strong resemblance to a small rat (and also Purgatorius from almost 100 million years later). It’s ankle joints were highly flexible and mobile for rotation characteristic of mammals living in trees. This is not seen in any other lineages of this era. It’s teeth indicated that this animal was an omnivore, well adapted to gnawing both plants and animals, including fruits, seeds, worms, insects and small vertebrates. Sounds like Rugosoden is even better suited to be a forerunner of primates than Purgatorius. It’s certainly not accepted by evolutionary biologists that rodents were a forerunner of primates but I think you may have something there Naan. Maybe we just don’t want to believe it?

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