Shemeska
Adventurer
As I recall, the arcanaloths were rewritten in Dungeon #149 ("Enemies of my Enemy") to be CR 17 creatures, with a note from the author saying that those are how arcanaloths "should" be.
I'm not certain if the ultroloths got similar treatment by Paizo; I seem to recall an updated ultroloth somewhere, but it might have been a fan conversion.
That was very much their intent, because they asked me for an editing pass wrt the 'loths in one of the 'loth heavy adventures (there was also a later one in one of the APs they took the opportunity to do a similar thing), since they had the chance to update their stats from the not exactly faithful to their 2e incarnations incarnations in 3e. It's been a while, so I don't remember much in specific.