User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4212769-20120302173919/@comment-4212769-20120309092806

You forget that Tigrex is the ancestor of all Wyverns (is described in its in-game description). And here in the wiki is said if you go to the Pseudowyvern site that they are the link between Elder Dragons and Wyvern. As Tigrex a ancestor of all Wyverns means that the Elder Dragons evolved first to Tigrex and Tigrex to other Wyverns.