The blurb on the back of the boxes states that 139 different Pokémon can be obtained in each game without trading. This, however, includes all Pokémon that the player must choose between (i.e., both the Omanyte and Kabuto families are counted). Therefore, the true total of different Pokémon obtainable in one adventure without trading is 124, which excludes the two unchosen starter families, one Fossil family, two Eeveelutions, one of Hitmonlee and Hitmonchan, and the four Pokémon that only evolve when traded.
Contributed by Funland47
Attachment
Attachment