Earth Sciences 1083F/G Lecture : Lecture 27 - Diversification of Mammals
26 Jan 2012
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Document Summary
Hadrocodium: few early mammals lived during the mesozoic, but were extinct by the early cenozoic y remaining therian mammals, 3 major group of living mammals, 1. mammals with placentas y reptiles to mammals hearing with our jawbones: evolution of ear: stapes acquires stirrup shape. more ear bones = more sensitive to sound: increasing sophistication of teeth as mammals evolve y evolutionary convergence, mammal groups show remarkable degree of evolutionary convergence. Process is slow by ecological standards because entire ecosystems have been destroyed beyond recognition, as many or even most species have gone extinct. Process is extremely fast by evolutionary standards, showing that exceptional conditions are in effect, promoting rapid evolution. link between the two factors is that ecosystems are reconstituted after mass extinctions. only had opportunity to take over after extinction of dinosaurs. goes against the survival of the fittest idea. ancestry on separate continents: no mosasaurs, ichthyosaurs or plesiosaurs survived the k-t extinction.
