User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-74.193.207.108-20121010154710/@comment-4212769-20121011064100

It could be a new Monster class as it's a new generation and a new generation normally has more than one new monster class. Maybe something like "Amphibian Wyvern", or so.

And only to say it: Actually Leviathans are Wyverns. Their Japanese name is translated "Sea Wyvern".