The Thought-Beast is a native endangered species to the dead planet Krypton. It resembles the Monoclonius dinosaur or a hybrid of the more widely known, triceratops and rhinoceros. It is unique however, in that the large bone-plate frill at the back of its skull is used as a projection-screen to connect the Thought-Beast with startling prey or intimidating predators alike. In addition, when in proximity to prey, they can cause violent hallucinations in prey, making them live some of their greatest fears. The animals are herd animals, and follow an alpha.
Thought Beasts were native to the Scarlet Jungle on Krypton. However, following Krypton's destruction, they were presumed extinct as with most of Krypton's native wildlife. Nonetheless, some survived. Superman has been shown with one in the Fortress of Solitude's Interplanetary Zoo, which has specimens of species from extremely endangered species, or species from destroyed worlds.
Kandor presumably had some as well. When it was enlarged into New Krypton, several Thought Beasts were reintroduced into the ecosystem. Suffering from starvation, they began rampaging through New Krypton, endangering its atmosphere generators. When Zod dispatched Commander Superman and his Red Shard unit to deal with them, Superman chose to order Red Shard to herd them rather than kill them.