Technically the asteroid didn't wipe out in that one shot, only the ones around what is today's gulf of mexico area. What wiped them out was the aftermath of the collision.
@Mustachekitteh that's still the asteriod killing them.
@OP that's still not the astroid killing it alone, it just played a small role in what actually happened. Then some people have speculated that the dinosaurs were already dying out before that happened and that the asteroid just made it worse. Which in that case means the main culprit was volcano's. news.nationalgeographic.com/.../
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