In XI tonberries were what became of the Kuluu (mostly), so they're essentially beastmen as they're not just mindless monsters, they have a society and were actually people during history at one point in time. (iirc, been 7 years since I did Zilart's storyline.)

They serve no true purpose, not even the Cryptonberries in the story aside being spirtual protectors, which is why most of the higher Tonberries/Cryptonberries are Summoners.