User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-74.193.211.56-20121116154743/@comment-4212769-20121116160242

Actually it can be opposed that Wyverns are still reptiles. They are evolved out of (the equivalent of) reptiles but could like mammals and birds in our world be already on a new evolutionary level (wrong word but I think you get what I mean).

Evidence:

1. They are warm-blooded unlike reptiles what mammals and birds that evolved from reptiles are, too.

2. They are very intelligent and specialized again like mammals and birds.

That's also the reason why dragons probably aren't reptiles anymore.

And with something the evolution of fur needs to begin. So those Pycnofibres or what they are in the end could be the earlier forms of pelt. Also mammals started from reptiles so that Narga is the link between Wyverns and mammal-like Wyverns (Fanged Wyverns) is plausible.