A simple question for ya to ponder.
To affect a human's body, you use corpus. To affect an animals body (and usually mind) you use animal. What art should you use to affect a mythological beastie that is part human, the most obvious example being a centaur.
Now, assuming the centaur is sentient, it's mentem to affect its mind. But what about the body? Animal or corpus?
Gremlin44 is right on the money. To expand the issue, to affect the whole creature would seem to be covered by the req. rules. St call if he's more man then animal, and then either (Creo, Rego, etc.)/Corpus(Animal) or /Animal(Corpus).
True - I've seen one "centaur-scorpion" magic being on tC&tC and their kin was one Magic Human but with Animal like Associated Form to his Might Score. He could be affected with Corpus to sick hime, but Animal to make him lame with one wound on the leg.