Unusued Red/Green Pokemon Concept

If you haven't seen, James Turner posted some pages from an upcoming manga about Satoshi Taijiri's life and the creation of Pokemone, and the images contain unused Pokemon concepts. The four clearest ones have been circulating and drawn a lot already, but I wanted to take a look at one that was kinda harder to make out. This is what I see in it. What do you all think? Rhyhorn prototype?

Pokemon belongs to Nintendo, GameFreak, and the Pokemon Company. This is just fan art. Please do not use without permission