User blog comment:Lord Loss/Discussion of the Week: Rare Species/@comment-22495647-20131205175201/@comment-4009941-20131205225454

Well technically there is 3 Rathians(4 more if you count HC variations and that odd Gold Rathian on frontier making that 7 variations), 3 Rathalos(3 more if you count HC and that odd HR100 one on frontier also making a total of 6 variations). That makes what? 13 variations of one monster? thats enough for me but always room for more!.

Zerureusu is related to Rathalos and is in fact a Rath and "UNKNOWN"(Yes thats its official name what you know as "Black Rathian" also) who is also another kind of Rath(Note is also has male rathalos features not just rathian) who is related to the main species we all know.

I think Rath's have the most variations in the series with all this.