I believe the PH is the Riparian Sahagin in the center of the room. It's usually a 2hr respawn after ToD. The Mermaid Tail is a 100% drop off Seww the Squidlimbed.
Ok, guys I soloed this as a DRG54/WHM27 and it popped in an open area next to the area in front of Utsusemi Area. Anyhow I soloed this guy after killing all of his buddies that dropped the other corresponding items for the quest. If you collect the Mermaid Hands, Feet, Tail, and Head and you talk to the gob that only pops on Windsday in Yuhtunga Jungle he will ask for them. You trade the to him and he gives you a Treasure Chest Marker on your map. Bring a Pickaxe and when you get to the area search for a ??? Use the pickaxe on tyhe ??? and you will open a coffer chest and the main item you get is a Mermaid Ring. I hope that helped someone ^^
Was campin Frog Trousers with a few friends and saw him pop on the ledge of L10. I was able to voke onto the lower lvl and of course whatever friends of his were near. Long fight insued. Him dead. His friends dead and we got this drop. Now could someone explain what we actually do with it?
You get the mermaid pieces, do some funny things with them and you're pointed to a treasure cove that has some nifty items in it, including enmity+ gear and other useful things. Very nice help for the NIN tank. PLD usually prefers VIT in their ring slots and all, but y'know.
You can do the same thing for other beastman types too. There's an antican treasure cache... Maybe a tonberry one. The Jiraat/Zilart-added beastmen have them.