User blog comment:Aandrew07/Discussion of the Week: Rage Mode/@comment-5029315-20131216151331/@comment-6050823-20131217000313

The UNKNOWN isn't a Rathian like you guys said but is closely related to the Raths. The same goes for Zerureusu but its unknown if its the UNKNOWN's mate or even if they are the same species though since it has been called "The 4th species of Rathalos" this could suggest otherwise. I do think they are different species from them being so different from each other but I could be wrong since afew monsters actually have extreme cases of sexual dimorphism like Generu Serutasu and Aruserutasu.