Community-reported
Based on player guides and/or gameplay footage, not confirmed directly from the game or the developer yet.
In co-op, keep track of who picked up the boss trophy item
A boss can drop meat, trophy pieces, and physics objects everywhere at once, and it's easy for a group to assume someone else grabbed the important one. Call out who picked up the trophy piece and make sure that player is present for the quest hand-in, before anyone starts selling.