Should "Hard Head, Big Teeth" for Oversized Goblins be 1d6 (1d8 with Savage Bite) or is the alternate racial trait 1d4 no matter the goblin's size?
It's not obvious to me how these three things interact:
Oversized Goblins are a Goblins Subrace:
Oversized goblins are Medium size, and grow to 4 to 5 feet tall. They tend to be particularly obese, weighing between 225 and 275 pounds. Instead of the normal racial ability score modifiers for goblins, oversized goblins gain a +2 bonus to Strength, a +2 bonus to Dexterity, and a –2 penalty to Charisma.
"Hard Head, Big Teeth" is a Goblin Alternate Racial Trait:
Hard Head, Big Teeth: Goblins are known for their balloonlike heads and enormous maws, but some have even more exaggeratedly large heads filled with razor-sharp teeth. Goblins with this trait gain a bite attack as a primary natural attack that deals 1d4 points of damage. This racial trait replaces skilled.
Feral Gnasher is a Barbarian Archtype for Goblins:
Savage Bite (Ex): At 1st level, a feral gnasher gains a savage bite attack. This is a primary natural attack that deals 1d4 points of damage. If the goblin already has the hard head, big teeth racial trait, the damage increases to 1d6. At 10th level, the damage from a feral gnasher’s bite increases to 1d6 (or 1d8 if the goblin has the hard head, big teeth racial trait) and deals ×3 damage on a critical hit. This ability replaces fast movement.