Dreadnoughtus, (meaning "fears nothing"), is a genus of sauropod dinosaur from the Late Cretaceous period which was discovered in 2005 and described in 2014. Being 70% complete, it is one of the more complete dinosaur finds of South America.
It was once thought to have been the heaviest dinosaur, and even heavier even than a Boeing airplane, however, it is now believed to have weighed 38,000 kilograms, and was 26m long. The holotype fossil is considered a juvenile, however, so its' likely Dreadnoughtus could grow much larger. Dreadnought was also the name of all battle ships with a uniform main battery of guns.
In Ark: Survival Evolved
Dreadnoughtus itself doesn't appear in Ark: Survival Evolved, however in the Brontosaurus dino dossier mentions that "Some may think this is an Apatosaurus, Dreadnoughtus, Argentinosaurus, or other sauropod - but this is a strange island and I'm the one doing the research" which means that people mistaken Brontosaurus for Dreadnoughtus and other sauropods that lived in the island. It's possible this could mean that Dreadnoughtus will be added to the game as a smaller, faster alternative to the Titanosaurus.