Did you know that Game Freak had thought of giving an evolution for Piloswine and Yanma in the second generation? Except then the developers change their minds in the development phase of the games and decided to cancel these two evolutionary lines, and subsequently invent in the fourth generation Mamoswine and Yanmega!
It is not the first time that such a thing has happened in the beta of gold and silver, in the demo of the Spaceworld 97 there were also the scrapped evolutions of Lickytung, Tangela and Leafeon, as well as the scrapped prevolution of Mr. Mime.
Curiosity: in the learn sets of Mamoswine, Yanmega and Tangrowth these Pokémon learn the second generation move: Acient Power, even if at least two of the three Pokémon do not belong to any ancient era, could be a reference to that "ancient or old period of development of Pokémon Gold and Silver where they were discarded. "
Source of this information:
https://tcrf.net/Development:Pok%C3%A9mon_Gold_and_Silver/Pok%C3%A9mon_Data/Cut_Pok%C3%A9mon 