I was wondering if Animal Fury Rage Power is Specifically required for the Dragon Totem Rage Power, or if you just need a natural bite attack. If the former, would there be any additional benefit from having both a natural bite attack through other means (Like the Razortusk feat or by virtue of being a Tengu) in addition to the Animal Fury Rage Power?
If it is listed as a pre-requiste which I believe it is then yes you must take it even if you have a bite attack from another source. of course if you have a more powerful bite attack from another source then you could still use it over the bite attack granted by animal fury.
but two things
first this is somthing you could negotiate with your GM as a house rule
second realise that not all pre-requistes are there to satisfy mechanical aspects of the next ability. sometimes pre-reqs exist to make taking the higher ability more expensive to take.
a good exaple of this is a feat that requires you take take skill focus in a knowlege skill as a pre-req which is a clear example of making the feat cost more though its pre-requisites.