<< Supposedly, the largest dinosaur to have existed was the Sauropod >>
Actually, Brachiosaurs, Diplodicus, etc (quadripedal long-necked herbivorous dinos) are all sauropods. It's a subgroup of the saurischian (lizard-hipped) group, which contains not only these huge plant eaters, but theropods such as Velociraptor and T rex.
Yes I know I'm a dork.