This didn't turn up in a search, so I'm asking now
AC Multiattack wrote:
An animal companion gains Multiattack as a bonus feat if it has three or more natural attacks and does not already have that feat. If it does not have the requisite three or more natural attacks, the animal companion instead gains a second attack with one of its natural weapons, albeit at a –5 penalty.Greater Ferocious Mount wrote:
While raging and mounted, the barbarian's mount gains the benefits of any rage powers that are constant in effect when the barbarian is raging. It does not gain the benefit of any rage powers that require actions to activate, even if they are free actions. A barbarian must have the ferocious mount rage power to select this rage power. A barbarian must be at least 8th level to select this rage power.
(Ferocious Beast is basically the same, except doesn't require you to be mounted)
How is this handled for an AC, such as a wolf that naturally only has a bite attack?
GFM potentially grants it additional natural attacks through beast or fiend totems, but it already gained a 2nd bite from AC-multiattack.
As I read the RAW, such an AC would get all the attacks since the effect of AC-multiattack is determined statically(compile time) once you hit effective druid level 9 rather than dynamically(run time) during each full attack sequence.