Are there any forms required other than the U.S. FWS form needed to import a warthog shoulder mount into the U.S.?

USDA may want to see it, It is mounted but sometimes they want to inspect it. Where is your port of entry? Boston? Call the USDA office at that airport and they will tell you. other then that, just your permits from the country of orgin, they will be with the shippment.