Natural weapon proficiency?

[rrwoods]

Many monster types explicitly mention proficiency with natural weapons (aberration, animal, dragon, elemental, giant, magical beast, ooze, plant, undead, vermin). However I'm having trouble finding any other mentions of proficiency with natural weapons. Of particular note, Totemist, Incarnate, Soulborn, and Warshaper all make no mention of it (I haven't checked the incarnum prestige classes but I suspect I'll find the same). Is a creature simply assumed to be proficient with its own natural weapons, even when it's only had them since the beginning of the round? Is there some rule that explicitly states this, or are we just assuming that class features that grant natural weapons don't come with this implicit drawback of nonproficiency?

[Psyren]

Pathfinder does say this explicitly. Not sure about 3.5.

[AllanniaNevini]

I'm not exactly sure but I would assume that creatures who aren't proficient wouldn't use natural weapons. Like a human wouldn't go up and bite someone as an attack, they would use a weapon of some kind

[rrwoods]

I'm not exactly sure but I would assume that creatures who aren't proficient wouldn't use natural weapons. Like a human wouldn't go up and bite someone as an attack, they would use a weapon of some kind

Right, sure, makes sense. So what happens when that human gets a natural weapon, say, as the result of using a soulmeld?

[Telonius]

The Bite of the Were-critter and several other lines of spells would have this issue too.

I don't know that it's ever explicitly stated. However there is an example character in Magic of Incarnum (p.157) that uses Girallon Arms. The statblock shows the claws' attack sequence and doesn't appear to contain a nonproficiency penalty. (I know, statblocks are notoriously inconsistent, but it's a published example).

I think it's pretty much assumed that all creatures are proficient in any natural attack they gain.

[Thurbane]

With the exception of Druid and one or two other cases, I don't think natural weapons are even called out as a type of proficiency, in the same way simple, martial and exotic are...