...did they exist? Without a doubt I'm sure. Why aren't they around today, still terrorizing the natural world? Cellular breakdown. Eventually the brain would rot to the point that it would become unfunctional. They would collapse and die like human s shot in the head. Could they have lead to the downfall of all dinosaurs 65 million years ago? Quite possibly. What if the meteor didn't hit, it just passed by close enough to raise the dinosaur dead.