I found the conversation about anthropomorphism rather fun, but you really can't treat evolution like that (already been said, twice). All an anthropomorphism function needs is to add/merge the traits Innominate listed (a slightly more specific and needs to include Religion though).
Someone already started a thread in relation to this.
I think most of them may be fictional or drawn from stuff like DnD because there aren't many true cave critters that aren't arthropods. Amphibians are already well represented in DF for subterranean, although a couple more wouldn't hurt.
Amphipods not exciting enough for you, eh? On another note, the slimes of D&D aren't as much of a stretch as you might think.
http://en.wikipedia.org/wiki/Snottite
That reminds of a time when the bath drain in the basement bathroom closed while it was draining. We learned of this a week later, and returned to find a bit of algae looking stuff growing in it. When I reached in to open the drain, I was met with a burning sensation, then a burning pain. Soap helped the hand, and bleach was used to clean the tub.
Oh, and some totally random things;
"001090 □ [weather] if rain lasts too long, ponds can overflow and flood the map" Why shouldn't there be flooding from excessive rain? It happens in real life. Buildings can be washed away and rivers overflow their banks.
"000802 □ [creatures] snakemen can get through fortifications" Wouldn't they be thin/contorting enough do that? Along with a few other creatures.
"000034 □ [dwarf mode][combat] sometimes attack an enemy while you're on a staircase above it can lead to you going down multiple floors when you charge" I can imagine just this happening with a single-direction landing spiral staircase. Where the momentum of the attack continues to push both stumbling parties down quite far. Why not just make it so both are bruised up and on the ground when this happens? To represent falling down stairs?