Arowana do have teeth it's just a matter of how big they are.. I had a baby, about 4 inches die and for some reason or another he ended up on top of the trash can outside... well after being outside and getting all dried up you could clearly see his little razor teeth. I don't know if they never grow anymore so they stay very small and you can't really see them.. I would estimate them to be around 1/32 of an inch but definately a lot of them not 3 or 4 like you see in some cichlids mouth a whole jaw of them...