User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-1758220-20110910042026/@comment-3298463-20110911173006

Pfft, I don't really know what can and can't be considered a "wyvern" anymore. Sometimes I get the impression that in-game it is used as a synonym of "monster". If I'm not mistaken even Lao was referred to as a wyvern in MH1 (or at least the name of its quest was something along the lines of "Giant Wyvern Invasion").

I just consider most reptilian monsters to be wyverns, even though by the strict definiton of the word only 2-legged ones should be.

And if I recall correctly, in one of the quest descriptions in Unite even Shen Gaoren was called a wyvern! Most likely a translation error, though.