The seismosaurus was a sauropod dinosaur. It was one of the largest land animals on Earth. It was more than one hundred fifty feet long and weighed over one hundred tons. It was a dull grey green. It lived in small to large groups, migrating to find food. The seismosaurus lived during the late Jurassic period.
The seismosaurus was one of the species that the Silurians brought back from extinction after they took over in a parallel world. Herds of seismosauruses roamed in the jungles of England. The Seventh Doctor and Ace hid in a herd of them to escape from Silurian hunters. (PROSE: Blood Heat)