The d20srd states, under Damage Reduction:
Some monsters are vulnerable to magic weapons. Any weapon with at least a +1 magical enhancement bonus on attack and damage rolls overcomes the damage reduction of these monsters. Such creatures’ natural weapons (but not their attacks with weapons) are treated as magic weapons for the purpose of overcoming damage reduction.
Does this mean that practically no other creatures' natural weapons count as magical for the purpose of overcoming damage reduction: X/magic, only that of those who explicitly have damage reduction: X/magic?