Smallest brained dinosaurs

The smallest brained dinosaurs are Stegosaurus (`plated lizard'), which roamed across Colorado, Oklahoma, Utah and Wyoming, USA about 150million years ago, measured up to 9m 30ft in total length but had a walnut-sized brain weighing only 70g 2.5oz. This represented 0.002 of 1 per cent of its computed bodyweight of 3.3tonnes (cf 0.06 of 1 per cent for an elephant and 1.88 per cent for a human).