Dreadnoughtus was a large titanosaur sauropod that lived in the Late Cretaceous period of South America. It is the most complete titanosaur ever discovered, and is widely considered the heaviest dinosaur to ever exist. The holotype fossil is considered a juvenile, however, so it's likely Dreadnoughtus could grow much larger.
Dreadnoughtus itself doesn't appear in the movies, although it appears as a viable embryo at the end of the film.
Dreadnoughtus can be created in the game. At first, it could only be obtained in the Jurassic card packs purchasable by real money. Since June 10th 2016, it became a DNA tournament limited edition.