Catchable Pokemon Number US/UM

[Full Crit Jester]

Ultra Sun is the first time back in Pokémon since X and I was wondering how many Pokémon are actually obtainable without trades or the bank on this cartridge alone?
I'm aware that there are 800+ in total now but realistically how much of that can I achieve from simply one game these days?

Any help understanding will be much appreciated!!

 

[Warrior of Fire]

I'd say your best bet would be to look up a reliable online list of the Ultra Alola dex and see what's exclusive to each game. I can easily say that with the exception of Aerodactyl, all of the fossil Pokémon are semi-exclusive. I say this because for the guaranteed fossils, half of them are available to buy ONE EACH of at Olivia's shop in Konikoni City. The ones there are game exclusive, although I'd have to look up which ones. However, you can get all of the fossils without trading with use of a fully-developed Isle Aphun at Poké Pelago in the rare item path. The only fossil I haven't gotten from there so far is the helix fossil, but that's only due not knowing what you'll get until you get the items.

 

[Bluemew1512]

In the game, there is 400 Pokemon in the alola pokedex. However, there is also 28 evolution lines that you can get through island scan and 20 lines that you get through ultra space ride. It’s also not considering in the Pokemon that are exclusive to a specific version and Pokemon that need to be traded to evolve, meaning that you have approximately 407 Pokemon that you can use. Check up a online guide though if you want to know the specific Pokemon you can find though.