Board Thread:General Discussion/@comment-765166-20131015174759

Unknown
Unknown (Black Flying Wyvern) is not a species of Rathian but in actuality an entirely different Monster. Think of it as Monoblos / Diablos comparison being similar in physique and move sets but an entirely different Monster. It is named this way as it is how its named in the game, with the (Black Flying Wyvern) part of the name being its Monster Title / Material.

Raviente and Violent Raviente
Raviente and Violent Raviente are NOT Elder Dragons. These monsters do not have a Monster Information entry in the game and therefore its classification is unspecified.

Zerureusu
Despite what fans and players alike think, Zerureusu is NOT an Unknown Species. The only Unknown Species in the game are Unknown (Black Flying Wyvern) and Mi Ru. Before Mi Ru was named, Unknown Species had the distinct feature to have no name in the game. Zerureusu has a given name, and it does not share the same mechanics with the other Unknown Species.

Also, Zerureusu is not the counterpart of Unknown (Black Flying Wyvern) due to it not being an Unknown Specie. 