GGR305H1 Lecture Notes - Lecture 7: Marsupial, Crown Group, Eomaia
12 Apr 2016
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Document Summary
Life into the present: mammals: intro to the quaternary. Mammals: when cenozoic started was huge opportunity for mammal evolution. Rise of reptilian precursors after kt extinction. A lot of reptiles survived extinction event: massive adaptive radiation of mammals occurring at beginning of cenozoic. Massive increase of species from single stem group: cenozoic can be considered as era of mammals. Early mammals evolved ~220 mya ago, pangea: evolved from therapsids in permian era. Oldest fossil: megazostrodon, rat/shrew-like creature, insectivore, had characteristics of early mammals, egg-laying but had ability to produce milk, wasn"t quite reptile but not quite mammal. Was also massive adaptive radiation in jurassic: radical change in body shapes occurring at high rate, mammals (including ancestors of marsupials and placentals) Even before dinosaurs died, mammals already evolving. Most mammals came up in cenozoic (even though early mammals present in mesozoic) 3 major mammal groups: placentals (includes us): 20 orders. Can carry their young to term (later stage of development)
