I've been asked to do a short presentation on it for my class, but honestly I've never heard of it. Apparently it's another theory about how the dinosaurs died out. If anyone knows anything about it, that would be very helpful
bravozulu
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That must not be the common name since there are few google hits on "plant emergence theory".
There are some theories that have to do with the rise of flowering plants and especially grasses favoring mammals. This guy talks about it. Most still seem to think that the impact wiped out the dinosaurs even when they acknowledge that the changing plants may have favored mammals.
http://www.wisegeek.com/when-did-grass-evolve.htm