Is it just a thread body with the two hackles?
Yeah, not the best picture in the world...

To answer your question, that's a Pearsall's black thread body with a little yellow Possum inserted, becoming thicker toward the ginger seal thorax. (Actually, the "purpose" of this fly was an experiment to find out what amount/kind/colors of dubbing would "pop" against a dark thread-base the way Ray's Conover Muskrat fly does.) As you can tell from my earlier comment, this doesn't appear to be it.
At any rate, this is the third fly I ever tried to use CDC as a secondary hackle so much works awaits, but I suspect that a CDC hackle wound by itself would either glom onto the hookshank (which would make a great thorax) or work as a "veil" for the primary hackle, depending on if you tied it on fore or aft.