Tyrannosaurus Rex, that huge hulking beast of a dinosaur, had serrated teeth, with the serrations running longitudinally up the tooth. Not much good for chewing, you might think.
One theory for why T-Rex had these saw-like teeth is that fragments of sinew and muscle from the dinosaur's most recent meal would get stuck in the serrations and rot. The bacteria would then provide T-Rex with a poisonous bite much like the Kimodo Dragon has today, so rather than having to administer a killing bite to its prey, T-Rex just had to take a passing nibble and let the toxins do the work.
If this theory is true, it does explain why T-Rex is so badly designed for a carnivore. Some studies have concluded that it was incapable of running at all and therefore must have been a scavenger, but if it had a toxic bite then speed would not be so important in order for it to be a successful hunter.