Does the sentence use modifiers correctly?

Scientists in Argentina discovered the bones of a titanosaur, an exceptionally large dinosaur heavier than fourteen elephants combined.

Yes, the sentence uses modifiers correctly. The modifier "in Argentina" describes where the scientists made the discovery. The modifier "an exceptionally large dinosaur" describes what a titanosaur is. The modifier "heavier than fourteen elephants combined" describes the size and weight of the titanosaur.