Is Ankylosaurus or Stegosaurus the smartest?

Stegosaurus had one of the smallest brain to body ratiOS of any animal known to have existed. Therefor, Ankylosaurus had a larger brain to body ratio. This does not necessarily mean that Stegosaurus were not as smart, however. The actual intelligence of an animal can not truly be determined by only fossils, because some animals are smarter than others that have larger brain to body ratiOS, although it is relatively rare.