See Appendages for the most recent listing.
All tails will add at least one Physical Damage attachment, regardless of critter. In addition, each tail type will give an additional Strength II T, when used on a specific species of critter. Here is a list of the different types of tails and which species each gives this "bonus" piece to.
Different Tail Types:
Bone Tail--gives Strength II T when used on a Steed
Lion Tail--gives Strength II T when used on a Wolf, Mammoth, Gorilla, Lion
Lizard Tail--gives Strength II T when used on a Lizard, Raptor, Crocodile, Dragon
Scorpion Tail--gives Strength II T when used on a Moth, Crustacean, Spider, Hornet, Mantis, Beholder
Spiked Tail--gives Strength II T when used on a Walrus, Tortoise, Cerberus
Stegosaurus Tail--gives Strength II T when used on a Toad, Wyrm
Tail Feathers--gives Strength II T when used on a Bird, Owlbear
Tail Fin--gives Strength II T when used on a Fish, Calamari, Hydra
All items (8)