no it actually probably had a large brain (which would be normal for its size)
About 500 grams. Roughly the size of an apple
The Stegosauruses cousin (like any other Dinosaur) is the lizard.
That sounds like a hedge apple. I use to call it a brain tree when I was a kid, because a hedge apple resemble a brain.
plants plants tree leaves
The size of an average apple is about the size of an adult Male's fist.
a stegasauruses brain is as big as a cats brain
plats
Stegosauruses is valid (http://en.wiktionary.org/wiki/stegosauruses), but so is Stegosaurus (http://www.memidex.com/stegosaurus+reptile-genus). The same way Fish and Fishes are both valid. Usage is the same as well.
apple size
2/3 of the size of an adult brain
what is the size of a 10mm leasion on the brain
Stegosaurus had a brain that weighed about 2.8 oz, the same as a dog's brain. An apple weighs almost twice that much. That is very small considering the fact that the Stegosaurus was 30 feet long and weighed 5.5 tons.