Left: T-Rex

Right:Tarbosaurus Bataar.

Tarbosaurus had a nasal enlargement on the top of its nose (See: Buran, Zdenek--Tarbosaurus) which served what to this day is still an unknown purpose. Maybe it was a horn boss, or anchor spot for a crest, who knows.

Anyway, T-bataar is also more distinctive because it is much more thoroughly represented by fossils through its entire life cycle than is its American relative.





Another idea may be:

Left: Male (Gracile)

Right: Female (Robust)

Even though few T-rex fossils are known overall, there are enough to postulate that the larger, more robust individuals were actually female. This makes sense when also considering the rex's closest living relatives, the birds. Among monogamous or pair-bonding birds like raptors, the females tend to be larger and stronger than the males, because they have to use their body-mass to live on while they're incubating eggs/tending young. The smaller, more gracile males would be the hunters. And in the case of T-rex, once the young are hatched and have grown to a sufficient size but are still light and swift, they help their father with the hunt by driving prey animals back to Big Mama, who administers the final blow.

Actually, I'd wager--