Not sure if anyone has posted this yet here... I could not find it on Hunter Forums.
Previously posted by "Inico" on the general WoD forums:Possible new "Thunder Hydra" models in WoD for the tamingA new hunter pet added in build 18164. It's a Thunder Hydra, similar to Megaera from Isle of Thunder (and all its files are in the same folder!). It has some mount animations (jump, mount swim, but no mount special), so it's likely to be a mount in the future!
confirmed by Jeremy Feasel: https://twitter.com/Muffinus/status/458708465397952513
http://www.wowhead.com/spell=160039 Hydra Pet Ability: Mastery