User blog comment:Lord Loss/Monster Hunter Frontier G 3 Discussion/@comment-8874090-20131006193441/@comment-765166-20131015180450

Since it is not a Rathian Species (which are a female-exclusive species), Unknown (Black Flying Wyvern) can be open to both Male and Female genders. The question is which, or if it can be both, or both at once. So the answer here is no one knows what its gender is unless an official source points to it.