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Lecture 13

Lecture 13 - Primate Evolutionary History - January 15.docx

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University of Toronto St. George
Keriann Mc Googan

January 15, 2013. Lecture 13 – Primate evolutionary history  Last period of the Mesozoic (Paleocene) is when mammals first appeared o Cenozoic the “age of mammals”  Primates, tree shrews, flying lemurs and bats are more closely related to each other than other mammals Some Definitions  Stem group: all taxa in a clade before a major speciation event o Don’t have the derived shared characteristics  Crown group: all of the taxa that come after major speciation event o Do have the derived shared characteristic  Sister group: two new clades that result from the splitting of a single common lineage Continental Drift  225 MYA all continents were one, called Pangaea  135 MYA there were two main continents, Laurasia (north) and Gondwanaland (south) o Dinosaurs were extinct by this point  65 MYA continents looked more like they do today, with some differences here and there  Important to study continental drift because of: o Where the continents are can effect climate and therefore the species of that area o Different environments (and species within) have to adapt to these gradual changes Climate Change  Global temperature changed in past 65 MY o First warmer and less variable, then cool and fluctuating temperature  In the peak warmth period of the Miocene palm trees could still be found as far North at Alaska Paleocene 65-55.8 MYA  A lot warmer than today’s worldwide climate, but still much colder than before Paleocene  Primate Origins (not true primates, but beginnings) o Paleontological evidence: first primates emerged in Paleocene o Molecular evidence: first primates as early as 90-80 MYA in Cretaceous period o Combined: 90-55.8  Molecular Clocks o Molecular anthropologists use genetics to investigate primate evolution o Compare DNA sequences to create a “gene tree” o Mutations occur at relatively constant rate of change  Therefore possible to estimate time between old species and new species o Amount of difference of two samples proportional to amount of time since LCA o Calibrated using fossil record  Primate-Like Mammals o Plesiadapiforms o 65-54 MYA o Classified as semi-order within the order Primates  Controversy around this  When first discovered they were thought to be part of the Primate order  But in 1960s it was decided that they weren’t part of the Primate order  Today we find they are a semi-order and have more in common with Primates than previously thought o Dental formula or  Similar teeth as Strepsirhines, but not at all same dental formula o Well-developed sense of smell o Six families Plesiadapiforms  Purgatoriidae o Purgatorius o Rat-sized,, primitive molars  Plesiadapidae o Plesiadapis o Marmot-sized, rodent-like incisors, primate-like molars and premolars, long snout  Carpolestidae o Carpolestes o Mouse to rat-sized, specialized dentition Eocene Primates  Euprimates: mammals with derived modern primate features o Adapoids: “lemur-like” o Omomyoids: “galago/tarsier-like” o Shorter snouts o Postorbital bar o More reliance on sight o Evidence that there were nails instead of claws  Family Adapidae o Lemur-like o E.g. Notharctus: North America, Adapis: Europe o Diurnal o Fruit and leaves o Arboreal quadruped o dental formula o Canines were sexually dimorphic o Evolution of true lemurs and lorises  Adapids did not have dental comb  Interesting due to basal position as sister group to all other primate lineages  Lorisoids in Fayum depression  Site in Egypt  Early ancestors of lemurs likely “rafted” over to Madagascar (at the time was not connected to Africa) on floating vegetation  Current back then went from Africa to Madagascar, rather than South through the channel like today  Subfossil lemurs  Megaladapis  Family Omomyidae o Three continents: North America, Europe, Asia
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