Seriously, have these tooth marked specimens been published? They
appear to provide important behavioral and paleoenvironmental data on
both T. rex and Triceratops. I'm puzzled, though. I can understand
why a Triceratops would fend-off an attack with its horns, but I am
struggling to understand why a T. rex would waste its energy biting
the horns of a Triceratops.
That one is pretty easy; the only manipulatory appendage a tyranosaur
has is its mouth, so if the Triceratops is trying to stab it with the
horns, or, just as likely, chunk huge holes in it with that
tree-chopping beak, grabbing the horns could easily be the best
available 'not getting poked or bit' option.
Could be an amazing wrestling match, considering the available strength
of neck on both sides.