|Wikipedia has an article about Seismosaurus.|
Seismosaurus, now recognized as a species of Diplodocus, was widely rumored to be included as a "hidden" or "secret" animal in Carnivores, along with Brachiosaurus, with the claim that one or both animals could be unlocked after earning 10,000 points. It was often suggested to be invulnerable to anything but the X-Bow, and that its only vulnerable spot was its eye, which was a seventh the size of the Tyrannosaurus' eye. It was also hinted to be carnivorous, or at least dangerous.
In reality, while either Seismosaurus or Brachiosaurus, or both, may have been planned for inclusion in Carnivores (and, indeed, Brachiosaurus was included in the sequel, Carnivores 2), neither animal is actually in the game, and there are no mentions of either of them in any of the game's files.
Status in Mods
Seismosaurus appears as the final huntable in the now-abandoned mod Carnivores Reloaded as the final huntable. It is an extremely aggressive sauropod that will forcefully stomp the player into the ground if bothered. The Seismosaurus in this mod is a light blue, in correspondence with the original myths. Unlike the myth which states Seismosaurus' mortal zone is the eye, Seismosaurus' mortal zone is not shown in Reloaded's hunt menu, as the animal is too dangerous to study. Reloaded's Seismosaurus has a few issues, such as occasionally freezing in place.
Seismosaurus makes a reappearance in Carnivores Reloaded's spiritual successor, Carnivores+, retaining its status as the final huntable animal. This iteration of Seismosaurus has more greenish-blue skin & has a chunkier build with its tail dragging on the ground, as it is based off Zdenek Burian's Brontosaurus. As with the old Seismosaurus, C+'s Seismosaurus is extremely aggressive & as such has no mortal zone data.
- Does Carnivores for PC has brachiosaurus's on it question on Answers.com