Does Nanotyrannus exist?

 Well it has long been known that Tyrannosaurus rex was the apex predator of its time and place with very little challengers to the title, but some paleontoligsts believe that another, smaller, faster tyrannosaur inhabited the area: Nanotyrannus,  the evidence is scarce, but its there so today we'll take a look at one of the most enigmatic dinosaurs ever to exist (or not).

 Evidence that it's a Tyrannosaurus sub-adult:

    If you really start to think about it there isn't that much evidence to support it being a sub-adult Tyrannosaurus other than the fact that the fossils aren't fully grown. We never actually found a tyrannosaurus juvenile for sure, the reason we think these bones come from a Tyrannosaurus is because we never actually found any bones that certainly come from a small Tyrannosaurus.

Evidence that it's a new species:

   Now, this is the more believable because there is a lot of evidence to support it. First is the different jaw count, Nanotyrannus had 17 teeth while T. rex only had 12-13, something we don't see any species do while maturing, is losing teeth. Nanotyrannus also had different brain shape than that of Tyrannosaurus, which means that while T. rex would look straight ahead, Nanotyrannus would probably have its head at a tilted angle. Then the most convincing piece of evidence i think is: Bloody Mary, the specimen known from the dueling dinosaurs fossil is the final nail in the coffin (I think). I mean there are so many things wrong with this if it was just a sub-adult T. rex, the fact that its taking on a Ceratopsian that size is shocking, considering the size difference, then the discovery of 30 steak-knife like teeth around the animals. Now we almost know for sure that Tyrannosaurus wasn't a solitary animal (weather it lived in complex packs like lions or family groups we don't know) as evidenced by trackways showing a T. rex group of different sizes walking together. If Bloody Mary was just a Tyrannosaurus sub-adult that died duringa hunt then don't you think we would find teeth matching those of Tyrannosaurus (or at least puncture wounds that would be adminstered by Tyrannosaurus). This means Bloody Mary hunted in a pack, with no adult Tyrannosaurs. 

Conclusion: 

   My conclusion is that Nanotyrannus was probably a different genus of Tyrannosaur, taking on a role comparable to that of a modern day Cheetah, while Dakotaraptor was probably the niche of a Leopard being more of an ambush predator rather than a sprinter. Anyway this is all just MY theory if you have any different Opinions please comment Below!