If you look at era specific screen shots of Legacy of Steel's Hoshkar kill, you will see that he CLAWS double and does not slash with the weapon on his table.
Source:
http://www.legacyofsteel.net/Archives/Post/2001-01-08
Attacking on the kill:
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Loot from the kill (slashing weapon):
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I also recall that a darkweed snake would always bite and never pierce, regardless of if it had the fang or not.
Here, you will see dragons like Hoshkar dual wielding weapons on their table incorrectly and creating an exponentially more difficulty challenge (Hoshkar, again used in example, can proc 640 cold dd like a boss with ranger wep... on a disease based fight..).
I believe this solves the animal/non-humanoid dual wielding debate. Mage pets and necro pets are specially flagged otherwise and will dual wield/double attack even without weapons. Such should be the rule, at least for non-humanoids.