Bird flu wiped out the dinosaurs?
Someone, I don't remember who, wrote a sci-fi novel to that effect.
The premise was along the lines of time travel being used to find out what got the dinos, lest something similar get us, and in the process a small dino is brought back, studied, then taken back to his home era having (unbeknownst to the scientist types) contracted parrot fever, or something like that.
So we killed the dinosaurs. Darn us.
= )