We have recently completed a MediaWiki update - There are a few issues that shall be ironed out in the coming day. Please be patient with any current errors.
Improved Natural Attack: Variant (3.5e Feat)
From D&D Wiki
Improved Natural Attack [General]
Prerequisite: Natural Weapon, Weapon Focus (chosen natural attack), Base Attack Bonus +4
Benefit: Choose one of the creature’s natural attack forms. The damage for this natural weapon increases by one step, as if the creature’s size had increased by one category.
Special: You can take this feat multiple times, the effects stack.