But it wouldn't have killed off all of the vegetation. If there had been a greater diversity of herbivores then more of them would would have survived, eating what was left. As far as lack of oxygen, I don't much think that would have been a major problem. At the present time the oxygen content of the air is just under 21%. Even if it dropped to 17% or so most animal life would have survived. The biggie would have been lack of food for the carnivores.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.