I received -- as a gift -- a small skull mounted on a carved wooden background, typical of Bavaria. I've looked online but am confused about US customs requirements. Can I bring this through? If not, and I declare it, will they just confiscate the item or will I just be fined?
You really shouldn't have a problem. From the CBP site:
For further concerns CBP refers you to APHIS for further information as this is an actual regulatory body responsible for import of animal byproducts:
However if you are concerned about it still you can ship it to yourself and avoid bringing it over the border on your own.