I agree with Paul (1988) and Carpenter (1992) that Tarbosaurus

is a junior subjective synonym of Tyrannosaurus (contra Rozhdestvensky, 1965).

Both species are united by the absence of a lacrimal horn (Carpenter, 1992), inflated descending paroccipital process, transversely-oriented occipital plate, and rostrocaudally restricted basisphenoid recess, among other features. A more detailed treatment of tyrannosaurid systematics is forthcoming.