Because this is wood, the details can be varied depending on my carving ability and the desired appearance. I usually smooth-sand the head instead of trying to simulate hair, and I try for an otherwise realistic look to the head, instead of a caricature.
After rough cutting the neck, I do a preliminary hollowing out of the peg box, especially where the D and A pegs insert. This can help to avoid damaging the head after it is carved, and allows for easier final hollowing later.
Next I carve the head, which sounds easier than it is. First of all, because of it's hair, when you look at a possum it appears that it has no neck and that the head just grows out of the shoulders. So, interpretation, proportion, and imagination are required to transition from the peg box of the violin neck into the head, so the look is satisfactory. After carving the long nose, eye recesses, and brow, I then carve the lower mouth and then the nose, which is kind of a gnarly looking thing, sorta like a combination of a pig and a horse nose, only much smaller. The ears can be challenge, because it never fails that no matter how accurate I make them, some critics will say they're not right, and yet when pressed they can neither describe, draw or carve them themselves. Anyway, what I do now is carve a set of ears and attach them to the head, instead of carving them from the block. This way, I don't need extra wood on the neck blank, the ears can be more realistic, they are stronger because I make them from dogwood and attach them cross-grained , and if they're not good enough I can easily try again.
Anyway, I've been polling friends and neighbors asking them what the animal is that I'm carving, and so far only my highly intelligent son has said "possum" right off. Of course, as yet it has not been detailed with color, but some responses suggest that folks need to get off their iphones and computers and go look at some wildlife.