Answer:
Step-by-step explanation:
The most appropriate example is the extinction of the dinosaurs. All sorts of theories were put forth. Most think there was a dramatic change in the environment, a change that left no time for the dinosaurs to adapt to that change.
Whatever happened, an asteroid, volcanic eruptions, or something else, whatever you propose has to explain why birds and mammals survived.
So whatever occurred, it had to be dangerous to land animals, but not those who flew or those who could think well enough to avoid whatever was happening around them.
That said, I would propose that it was a virus that was not air born and the genetic make up of mammals could avoid the harmful effects of the virus.
I would propose that this is the only explanation that works. Perhaps the makeup of the blood could not adapt to the extinction. The blood of a dinosaur might not have included very powerful neutrophils (which fight disease).