This API call should bring back active ungrafted species: https://api.inaturalist.org/v1/taxa?is_active=true&parent_id=0&rank=species
But it’s also bringing back a taxon which doesn’t seem to exist (Mammillaria estebanensis, 1143041):
Attempting to get to https://www.inaturalist.org/taxa/1143041 gives the search mole:
Note that there is a Mammillaria estebanensis that exists, but it’s 1143040. It seems someone tried to import it twice in rapid succession.