which part of the tail are you looking to make? if you want to make a fin you can use the butterfly wing tutorials, and the rest of the tail I make using tin foil and apoxie sculpted over the top, I normally cut the back legs off first and form a tail shape out of tin foil and glue in place with a hot glue gun then place a layer of apoxie over the top smoothing down as I go along and place in a position I like and leave to dry over night, the next layer can either be done scaled or you can smooth more clay on and add a pattern. hope this helps.