Say farewell to Oxalaia and Sigilmassasaurus.

[Sim]

because there are like no giga fossils and the ones we have are very poorly described

Fossilisation is a very rare event, the reason there are so many Tyrannosaurus specimens is because of their high commercial value resulting in more searching for specimens.  I have no idea what being "very poorly described" has to do with this.

How do we know Giganotosaurus didn't have "a stupid huge range" too?  Also dinosaurs including non-avian theropods had to migrate for different species to occur in different formations.

[Dealt with above]
also that second point is completely wrong

A creatures range expanding isn't migration. Migration is seasonal movements between regions.

In response to these two quotes, I've just looked up "migration" and one of its meanings is "movement from one part of something to another."  So I stand by migration being necessary for non-avian theropods too.

[Dynomikegojira]

I think the neutral argument to be made here is that is it possible an hypothetical undiscovered Giganotosaurus species could have lived in Brazil alongside Oxalaia well perhaps I'd more likely consider it a Carcharadontosaurus depending on if North Africa was closer to Brazil than either would be to Patagonia admittedly just my theory but kinda supported that both Brazil and North Africa had similar ecosystems. Likewise could a spinosaurid coexist with Giganotosaurus in Patagonia I'd say maybe along the coastal regions but the truth is we may never know until new discoveries and there's not much wrong into reasonable speculation.