>let me point to a well-known
> nominative which certainly looks marked:
> Lat. nom. Juppiter
That depends how real it is as a declensional form. I'm sure you are aware
that it is simply the stem iou + s, followed by the word "father". The
nominative also exists without the "father" bit, as Iovis. I don't know
offhand any examples of oblique cases with "father" but I would be surprised
if we can't find them. That means that Juppiter is merely a frequent
collocation, not a "marked nominative" form.
Peter