Comment on Puertasaurus reuili by Paleo-King

Perhaps. Though Mapusaurus is more likely to have been a "mob hunter" than a pack hunter (i.e. they were not too terribly organized.) Carcharodontosaurids in general have very primitive brains considering their huge size and relatively late age. In some ways their mental hardware was no more sophisticated than that of the smaller allosaurs that lived in the Late Jurassic, which may have been pack or mob hunters (we can't really tell due to gatherings of allosaur skeletons at particular sites being largely artifacts of predator traps, hence biasing the apparent "message" of the fossil record in those places). Overall it's believed that Carcharodontosaurids survived because their prey was just sauropods which were not all that fast or maneuverable, so it wasn't really necessary to coordinate much pack strategy to catch them. You only need to be smart enough to catch your prey.

The problem with attacking an adult giant titanosaur is that they're very large and more robust than most other sauropods. Also the armor, when it was present, made them very hard to attack. Giganotosaurus and its kin were not equipped to bite through armor, their teeth were the narrow, sharp slashing kind, not the huge blunt armor-cracking kind like T. rex. Theu would have gone for the animal's weak spots like the neck, which is much easier to reach in juvenile sauropods than adults. Also keep in mind that despite being longer than T. rex, Giganotosaurus and its relatives were not as tall, they were all pretty low-slung and their necks were not so strongly s-curved as tyrannosaurs, so their lack of vertical reach means they had a hard time getting to the necks of large sauropods, but had no difficulty targeting small ones. All the same it would make an epic scene, as would an attack on the younger members of a herd that also included the huge adults.