For some reason, I went to look up kangaskhan, and the links at the top which navigate you to the Pokémon before and after it on national dex number was both tangelas and had ??? as the number! Both lead to tangela. Then on tangela page it was both chansey with ??? as the number too! It was the same with most pokemon, what is going on?
Oops, I meant to put ??? only for the new Pokemon from X/Y. I have fixed this now so it works for all Pokemon.