The Knifetooth Sawfish, the only species in its genus within the small family Pristidae that is the only family within the order Pristiformes. Rather unusual, in other words. This is another large (up to 6 meters) mostly-harmless species; they don't attack humans, but the teeth imbedded in the outside sides of the jaws can cause serious injury if one of these is caught, as they tend to thrash violently (not surprising, given a hook in the mouth).
They're related to the sharks and rays, in the Class Chondrichthyes, SubClass Elasmobranchii, Division Neoselachii, Subdivision Batoidea - in other words, they're rays, though they don't particularly look like other rays.
Sorry about the poor-quality, small picture - it was the only one I could find.