The Latin genitive plurals in -rum are very noticeable in the paradigm. Be it first declension in -ārum, second in -ōrum, or fifth in -ērum, they are heavyweight, attract accent and basicall stand out among other forms. Unfortunately, in the Romance collapse of case forms, it were the accusatives (and rarer nominatives) that survived.
But are there any forms in Romance languages that are directly descended from the genitive plurals? I am looking for the inflectional forms first, as they would be more interesting than singular fossilized explessions (though I am wondering about those singular fossilized explessions as well).
Feel free to resend the question to Latin StackExchange if you feel it could be better answered there, but I expect this question requires more expertise in modern Romance languages and so is for here.