Stegosaurus
Stegosaurus, name meaning roof lizard, was named for the distinctive 2 rows of plates that ran down its back which are theorised to be used for display or thermoregulatory purposes. The creature has an extremely low brain to body ratio, with a brain the size of a walnut but makes up for this with a heavily built, 9m long body and a bone shattering thagomiser at the end of its tail. This could be swung at predators like Allosaurus and Ceratosaurus who dared threaten the gentle giant as it fed on the late jurassic flora.