Just one disturbance - a small meteorite impact or even a fast moving mammal - could then have brought the gas-saturated water closer to the surface. So, the mass extinction could have been caused by a mammal. Fish are NOT implicated, everyone! No need to panic! No fish, no reptiles are responsible for this catastophe! It's either an asteroid, or a mammal, and we're betting it's a mammal -- they always mess up the environment.
Yeah, the mammal reference is a bit weird since they (we) don't appear in the fossil record till almost 200 million years later. Maybe he meant to say "even a fast moving motor home" since everyone knows big vehicles are the ultimate source of all doom.