Is this fish Kosher? It apparently has both fins and scales. Is there any problem with its having teeth, or its not having been discovered until now (and therefore being outside of our Mesorah)?
Teeth aren't an issue - unlike with land animals and birds, kosher fish can be predators. (In fact, barracuda is kosher - and you don't get much more toothy than that!)
Fish don't need a mesorah to be kosher (unless it's a corner case, such as where it's uncertain whether the scales are detachable from the skin, or where it resembles too closely a non-kosher species - see Where is the story of the medieval rabbi who ruled a fish was non-kosher because of his dream?). So provided that this fish's scales are of the kosher type, it sounds like it would be okay.
Even small scaly finned fish have little teeth, the teeth are not any problem to defining kosher in fish. The scales and fins look good, so its kosher fish. Its size is not a problem.