Note, however, that the bison is not optimized for speed and quickness, but for strength and ruggedness, which suggests (in my mind, at least) that it was not adapted to deal with tyrannosaurs.
Ruggedness - as in "Can live in temperatures much below freezing".
Might it not very well be the case that bison and T-rex were often climatically isolated? They trod the same ground but not at the same time of the year?
I just don't see T-rex hanging out in a Montana winter. Or were the winters much milder =/- 5000 years ago?
Moose
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