EARLY PRIMATES When do we see the earliest primates Eocene 55 mya earliest undisputed primates However we already see some variety at this time indicating that primates began earlier despite our lack of clear fossil evidence 55 mya 65 mya Paleocene 65 55 mya Dinosaurs are extinct temperatures rising North America Europe pulling apart islands between Geoknow net Major mammal radiation to fill niches left by dinosaurs Some of the small mammals are primate like or primitive primates or archaic primates EARLY PRIMATELIKE MAMMALS or archaic primates occur in what became North America and Europe which at that time were tropical 65 mya Montana primatelike teeth 60 mya Wyoming a few bones example Plesiadapis CreationvsEvolution PaleoceneMammals Plesiadapiforms early Paleocene to late Eocene Known mainly from North America but also found in Europe and China Controversy over whether primates or not Range from mouse size to small monkey sized Anatomically more primitive than any living primate Plesiadapis is one example Why aren t we sure when the earliest primates appear 1 Incomplete fossil remains mostly teeth jaws some skull fragments 2 Differences among scientists on how to classify some consider them experiments in becoming primates but still just primatelike mammals Plesiadapiforms don t have even the characteristics of living prosimians Thus they are called archaic primates Plesiadapiforms Small brains prognathic face small eye sockets on the sides rather than front of head no postorbital bar and many have rodent like incisors separated from the molars by a large diastema Some have claws and lack an opposable big toe Range in size from mouse to cat Geologic Time Scale ERA Period Epoch 1 7 mya GLACIATION Ice Age 5 mya Central America joins N S 24 mya 36 mya N America Asia begin split S America Africa separate 55 mya Plesiadapiforms 65 mya http www ucmp berkeley edu cenozoic cenozoic html 22 Feb 2005 Eocene 55 36 mya Very warm even in the north formation of rain forests Climate change accompanied by replacement of the archaic mammals of the Paleocene with mammals of modern aspect Laurasia doesn t separate until middle Eocene First undeniable primates are found in North America Europe Africa and Asia These are prosimian like at least 60 genera in two main families Peak of prosimians Why does everyone agree these are primates Slightly larger brains than plesiadapiforms Eye sockets on front of face stereoscopic vision and depth perception Postorbital bar protects the eye socket Opposable big toe Nails rather than claws Reduction in snout Eocene continued 55 36 mya Two main superfamilies of primates 1 Adapids which continued as Prosimians and 2 Omomyids which became Anthropoids and tarsiers Based on molecular data it is thought the split between Prosimians and Anthropoids actually took place around 58 mya during the Paleocene but we don t yet have many good fossils to prove that Eocene 55 36 mya Adapiformes Adapids Lived in North America Europe Asia Africa The most primitive group of early modern primates Probably ancestral to present prosimians such as lemurs Had dental comb for grooming Some nocturnal some diurnal Ate leaves folivores Arboreal Sense of smell Small to medium up to 15 lb Biological Anthropology 2006 Stanford et al 272 Eocene 55 36 mya Omomyids lived in North America Europe Asia Probable ancestor to tarsiers and anthropoids Size of squirrels up to 5 lbs Nocturnal Ate fruit and insects shorter snout Visual predation theory Necrolemur Biological Anthropology 2006 Stanford et al 272 Theory about why primate characteristics developed Visual Predation Theory Searching for fruit and insects on slender branches favors vision especially forward facing eyes over smell grasping hands and feet and nails instead of claws Geologic Time Scale ERA Period Epoch 1 7 mya 5 mya 24 mya 36 mya 55 mya 65 mya http www ucmp berkeley edu cenozoic cenozoic html 22 Feb 2005
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