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Lecture 27 - Paleoprimatology

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Esteban Parra

ANT203Y5 – BiologicalAnthropology Lecture 27 – March 4, 2014 Paleoprimatology The First Primates - The evolution of primates can be traced back to the late Cretaceous/early Paleocene. Primates probably evolved from a small, ground-dwelling shrewlike insectivorous mammal. The Origin of Primates - Probably, the earliest primate ancestors looked like the tree shrew depicted below. o The tree shrew are the closet relatives to the primates - Recall that there was a mass extinction around 65 mya (Dinosaurs disappeared). It was the beginning of an adaptive radiation of placental mammals Purgatorius - 60 million years ago o Old fossils found in Montata, USA o They are not primates yet, but they are on the line on their way to being primates o These are one of the first mammals that we can put into the lineage that will eventually become primates - Probably, there was a shift in diet from insects to fruits and seeds. This is evident in some fossils from the late Cretaceous, such as Purgatorius. The Paleocene: Plesiadapiforms - 65 million years ago - The fossil record indicates the presence of squirrel-like mammals, the plesiadapiforms, with very specialized dentition. o For a long time, they were considered to be order primates, but not anymore o This is the case because they have derived characteristics that are different from things that you see in primates o They are already specialized in one direction, and for this reasons, people think they are not the ancestors of primates o So they are not primate, but very close (therefore a different order) - Plesiadapiforms differ, in many ways, from modern primates, and are classified in a different order (Plesiadapiformes) Why are they not considered primates? - There are evidence where they have characteristics that are primitive - It is believed they have claws, and don’t have oppositable toes (so primitive compared to other primates) - This includes a large gap in the diastema (which isn’t found in primates, including early primates) - They have quite unique, and large incisors that are incline, with the gap separating from other teeth - Primates (even lemurs) have the postorbital bar, but the Plesiadapiforms do not - This sets this aside from other primate Eocene, the First Euprimates ANT203Y5 – BiologicalAnthropology Lecture 27 – March 4, 2014 - In the Eocene (54 to 38 mya), many plesiadapiforms went extinct, and were replaced by the first primates, which were very much like modern prosimians. - There are fossils resembling modern tarsiers (Omomyds), and fossils resembling modern lemurs (Adapids). o Adapids: have traits that puts them aside (or closely related to) the lemurs. They are beleieved to be dinurnal. But this is a diverse group, there are exceptions. They have similarities to present day lemurs o Omomyds: they are different from adapids. They tend to have large orbids, and for this reason they are believed to be nocturnal (for the most part). They have a shorter face in comparison to adapids. They are considered to be related to haploarmids (tarsiers). o These are true primates The Origin of Anthropoids - There has been quite a lot of controversy regarding the origin of Anthropoids. o For some researchers, they evolved from Omomyds (tarsier-like forms) o Other anthropologists believe that they evolved from Adapids (lemur-like forms) o Others believe that they could have evolved from an independent, still unidentified group. Fayum - This is a rich anthropoid fossil site in Egypt, which has been dated back to the late Eocene and early Oligocene. o 38 -23 mya Early Oligocene Anthropoids in Fayum - Four anthropoid groups are present in Fayum: o Propliopithecidae. Larger in size and with advanced traits (such as 2 premolars), shared with Old World Monkeys. o Parapithecoidea.Adpidium o Proteopithecidae. Aegyptopithecus o Oligopithecidae. o The last three groups, there is no clear evidence how they are related, or who exactly WhatAbout the Primate Discovery of the New World? - The origin of the New World monkeys is also controversial. - There are no primate fossils in SouthAmerica from before 30 mya. After this period, Anthropoids are found in the fossil record (Branisella, Dolichocebus). ANT203Y5 – BiologicalAnthropology Lecture 27 – March 4, 2014 - SouthAmerica was separa
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