Giganotosaurus skull

[kodiak@INETWORLD.NET (MC2)]

    I haven't read all my posts so excuse me if this is going over old
territory.

      Concerning Giganotosaurus, I was struck by the robustness of the
ridges on either side of the skull, running from behind the nares to (I
think) above the orbits.  I only saw a blurb on CNN, so I couldn't tell:
Are these part of the maxilla or the nasal? Are there any other theropods
that even approach this level of (robust) skull ridge construction?
     I can think of no other function for these structures except for
head-butting, but I suppose display could play a part.  (The artist's
reconstruction just seemed top blow off this feature.)  Are there any
modern analogues for this type of ridged skull architecture?

     Thanks,