Name all the Pokemon in Generation I that DO NOT have a variation, regional variation, convergent species (including Paradox), mega evolution, Gigantamax, split evolution, added evolution in a later generation, etc.
Added evolutions only include the pokemon evolved from or evolved to, not the whole line. i.e. Dusclops would not be forgotten because it can evolve into Dusknoir in a later generation. Duskull would be forgotten as it has no new direct evolution.
Regional variants do not count as split evolutions
Blog with explanations - https://www.jetpunk.com/users/kidibu/blog/forgotten-not-pokemon-explanations