you both co-produced it - that is the meaning of co-produced joint production
i.e. neither one of you is the sole producer of the work
are you sure that you are not arguing about splits/points instead -again it should be 50/50 if you both contributed to the production equally
good rule of thumb for the future establish the splits before not after and keep a camera rolling to capture who did what in case of future disputes - call it security footage or whatever, but do yourself a favour and make sure that you document the process from start to finish to stave off any future squabbles about who is what.....