Pretty sure wyvern tails don't drop. This breaks the quest with The High Ravenfather in Zhentil Keep.
Tested:
a wyvern - flies north of ZK and in the Forest of Wyrms
a greater wyvern - Forest of Wyrms
an ancient wyvern - tower west of Zhentil Keep in the centaur area
Wyvern Tails don't drop
Wyvern Tails don't drop
Glim asks Gwain 'Can I be on the watch?!?'
Gwain raises an eyebrow.
Gwain seems to display a look of complete horror for a second...
Gwain raises an eyebrow.
Gwain seems to display a look of complete horror for a second...