Apceros are large herbivores reminiscient of ankylosaurus or similar dinosaurian relatives. They are also very aggressive and will attack you without warning first by slowly and creepily stalking you (seriously, it's unsettling if three or more are slowly walking towards you). Then they will headbutt you, or try to whack you with their clubbed tails. Very irritating! Just go ahead and take them out if you can afford to, as they don't have much health just like any other little herbivore.