Dangerous rhino-sized animals that inhabit the Scarlet Jungle of Krypton. Vaguely resembling the dinosaur Triceratops from Earth, Thought-Beasts differ in being smaller, aggressive -- and possibly partly carnivorous, and in having a head frill made up of a large "video screen" that projects the dreams and intentions of the creature from an outside perspective. Practically all humanoid meetings with angered Thought-Beasts lead to the "video screens" projecting the demise of the person in the animal's jaws.
A Thought-Beast turns up on Earth and battles Superboy, in this case the animal escapes from alien zoo keepers who had abducted it from Krypton before the destruction of the planet. (SB No. 102, Jan 1963: "The Secret of Krypton's Scarlet Jungle")
Another example of an encounter with a Thought-Beast occurs when Superman journeys with temporarily paroled Phantom Zone prisoner Jax-Ur to find a fungal spore in the Scarlet Jungle of Krypton's past. In this case, a large mushroom thrown against the frill of the Thought-Beast appears to break its train of thought. (Act No. 310, Mar 1964: "Secret of Kryptonite Six!")