User blog comment:- MHCaboose -/Monster Hunter Frontier Z Discussion/@comment-6050823-20160830013610

I did a bit more research and I now kinda get the Zenith Species.

Unlike normal species, the Zenith Species have greatly developed a certain portion of their body more and this allows them to deliver deadlier attacks than usual. By destroying said portion (Head, pincers, wings, etc.), this gives hunters an instant rare drop.