Dreadnoughtus are shown fighting by slashing each other with their giant thumb claws. Titanosaurs, the group which the animal belonged to, generally did not have thumb claws. The show's creators were aware of this, but chose to depict Dreadnoughtus with claws because another titanosaur, Diamantinasaurus was found to have had thumb claws. During production, it was deduced that this animal would have been very distantly related to Dreadnoughtus, and Dreadnoughtus most likely had no claws on its front feet. By that time it was too late to change the CGI models, so the incorrect claws were kept.
Scientific consultant Darren Naish explained that the dinosaur named Velociraptor in the series was not technically meant to be the genus Velociraptor, but rather an unspecified close relative of it, as Velociraptor had gone extinct about 5 million years before the series is set. They just called it Velociraptor for convenience's sake.